diff --git a/src/Helper.php b/src/Helper.php
index f5e9901..cb566ea 100644
--- a/src/Helper.php
+++ b/src/Helper.php
@@ -5,14 +5,15 @@
  * Contains base methods that all messages will use.
  */
 
+use Closure;
+use DateTime;
 use Exception;
+use DateTimeZone;
+
 use UnexpectedValueException;
 use Psr\Http\Message\MessageInterface;
 use Psr\Http\Message\ServerRequestInterface;
 
-use DateTime;
-use DateTimeZone;
-
 abstract class Helper
 {
     // SagePay date format, ISO 8601 with microseconds.
diff --git a/src/Request/AbstractRequest.php b/src/Request/AbstractRequest.php
index fb4a0e4..188b73b 100644
--- a/src/Request/AbstractRequest.php
+++ b/src/Request/AbstractRequest.php
@@ -13,6 +13,7 @@
 use Academe\SagePay\Psr7\Factory\FactoryInterface;
 use Academe\SagePay\Psr7\Factory\DiactorosFactory;
 use Academe\SagePay\Psr7\Factory\GuzzleFactory;
+use Academe\SagePay\Psr7\Factory\RequestFactoryInterface;
 use UnexpectedValueException;
 use JsonSerializable;
 use Exception;
@@ -179,7 +180,7 @@ protected function setFactory(RequestFactoryInterface $factory)
     protected function withFactory(RequestFactoryInterface $factory)
     {
         $clone = clone $this;
-        return $clone->setAuth($factory);
+        return $clone->setFactory($factory);
     }
 
     /**
diff --git a/src/Request/CreatePayment.php b/src/Request/CreatePayment.php
index 983fbbe..77b3222 100644
--- a/src/Request/CreatePayment.php
+++ b/src/Request/CreatePayment.php
@@ -12,6 +12,8 @@
 use Academe\SagePay\Psr7\Model\Auth;
 use Academe\SagePay\Psr7\PaymentMethod\PaymentMethodInterface;
 use Academe\SagePay\Psr7\Money\AmountInterface;
+use Academe\SagePay\Psr7\Request\Model\AddressInterface;
+use Academe\SagePay\Psr7\Request\Model\PersonInterface;
 
 class CreatePayment extends AbstractRequest
 {
@@ -263,10 +265,9 @@ public static function getApply3DSecures()
     }
 
     /**
-     * @param ShippingAddress $shippingAddress
-     * @return Transaction
+     * @return self clone
      */
-    public function withShippingAddress(ShippingAddress $shippingAddress)
+    public function withShippingAddress(AddressInterface $shippingAddress)
     {
         $copy = clone $this;
         $copy->shippingAddress = $shippingAddress;
@@ -274,10 +275,9 @@ public function withShippingAddress(ShippingAddress $shippingAddress)
     }
 
     /**
-     * @param ShippingRecipient $shippingRecipient
-     * @return Transaction
+     * @return self clone
      */
-    public function withShippingRecipient(ShippingRecipient $shippingRecipient)
+    public function withShippingRecipient(PersonInterface $shippingRecipient)
     {
         $copy = clone $this;
         $copy->shippingRecipient = $shippingRecipient;
diff --git a/src/Request/CreateRepeatPayment.php b/src/Request/CreateRepeatPayment.php
index 6e2e8cb..c0e014a 100644
--- a/src/Request/CreateRepeatPayment.php
+++ b/src/Request/CreateRepeatPayment.php
@@ -12,8 +12,9 @@
 use Academe\SagePay\Psr7\Model\Endpoint;
 use Academe\SagePay\Psr7\Model\Auth;
 use Academe\SagePay\Psr7\Money\AmountInterface;
-use Academe\SagePay\Psr7\Model\AddressInterface;
 use Academe\SagePay\Psr7\Model\PersonInterface;
+use Academe\SagePay\Psr7\Request\Model\AddressInterface;
+use Academe\SagePay\Psr7\Request\Model\PersonInterface as ModelPersonInterface;
 
 class CreateRepeatPayment extends AbstractRequest
 {
@@ -29,6 +30,7 @@ class CreateRepeatPayment extends AbstractRequest
     // Optional or overridable data.
     protected $shippingAddress;
     protected $shippingRecipient;
+    protected $giftAid;
 
     /**
      * @var string The prefix is added to the name fields when sending to Sage Pay
@@ -87,7 +89,7 @@ public function __construct(
      * @param ShippingAddress $shippingAddress
      * @return Transaction
      */
-    public function withShippingAddress(ShippingAddress $shippingAddress)
+    public function withShippingAddress(AddressInterface $shippingAddress)
     {
         $copy = clone $this;
         $copy->shippingAddress = $shippingAddress;
@@ -98,7 +100,7 @@ public function withShippingAddress(ShippingAddress $shippingAddress)
      * @param ShippingRecipient $shippingRecipient
      * @return Repeat
      */
-    public function withShippingRecipient(ShippingRecipient $shippingRecipient)
+    public function withShippingRecipient(ModelPersonInterface $shippingRecipient)
     {
         $copy = clone $this;
         $copy->shippingRecipient = $shippingRecipient;
diff --git a/src/Request/FetchInstructions.php b/src/Request/FetchInstructions.php
index c0cdeae..f44028c 100644
--- a/src/Request/FetchInstructions.php
+++ b/src/Request/FetchInstructions.php
@@ -18,5 +18,6 @@ class FetchInstructions extends AbstractInstruction
     #[\ReturnTypeWillChange]
     public function jsonSerialize()
     {
+        return [];
     }
 }
diff --git a/src/Response/AbstractCollection.php b/src/Response/AbstractCollection.php
index 8541006..83580d8 100644
--- a/src/Response/AbstractCollection.php
+++ b/src/Response/AbstractCollection.php
@@ -2,11 +2,14 @@
 
 namespace Academe\SagePay\Psr7\Response;
 
+use ArrayIterator;
+use IteratorAggregate;
+
 /**
  * A a collection of instructions.
  */
 
-abstract class AbstractCollection extends AbstractResponse implements \IteratorAggregate
+abstract class AbstractCollection extends AbstractResponse implements IteratorAggregate
 {
     /**
      * The list of items.
@@ -22,6 +25,7 @@ abstract class AbstractCollection extends AbstractResponse implements \IteratorA
     /**
      * @return ArrayIterator
      */
+    #[\ReturnTypeWillChange]
     public function getIterator()
     {
         return new ArrayIterator($this->items);
diff --git a/src/Response/AbstractResponse.php b/src/Response/AbstractResponse.php
index 003a200..92833e5 100644
--- a/src/Response/AbstractResponse.php
+++ b/src/Response/AbstractResponse.php
@@ -24,6 +24,8 @@ abstract class AbstractResponse extends AbstractMessage implements Http, RFC4918
      */
     protected $httpCode;
 
+    protected $status;
+
     /**
      * Can initialise with a PSR7 message, an array, a value object or a JSON string.
      *
diff --git a/src/Response/InstructionCollection.php b/src/Response/InstructionCollection.php
index e45dcca..a6c9b7e 100644
--- a/src/Response/InstructionCollection.php
+++ b/src/Response/InstructionCollection.php
@@ -16,9 +16,6 @@ class InstructionCollection extends AbstractCollection
      */
     protected $permittedClass = AbstractInstruction::class;
 
-    /**
-     *
-     */
     public function setData($data, $httpCode = null)
     {
         if ($httpCode) {
@@ -37,6 +34,8 @@ public function setData($data, $httpCode = null)
                 $this->add(ResponseFactory::fromData($instruction, $httpCode));
             }
         }
+
+        return $this;
     }
 
     /**
diff --git a/src/Response/NoContent.php b/src/Response/NoContent.php
index 434bbd4..442e954 100644
--- a/src/Response/NoContent.php
+++ b/src/Response/NoContent.php
@@ -11,10 +11,12 @@
 class NoContent extends AbstractResponse
 {
     /**
-     * No data to set (this is an empty messgae body).
+     * No data to set (this is an empty message body).
+     * @inheritDoc
      */
     public function setData($data)
     {
+        return $this;
     }
 
     /**
diff --git a/src/Response/SessionKey.php b/src/Response/SessionKey.php
index 33701ae..05ad608 100644
--- a/src/Response/SessionKey.php
+++ b/src/Response/SessionKey.php
@@ -81,7 +81,7 @@ public function isValid()
         }
 
         // Do we have a 404 HTTP response code recorded?
-        if ($this->getHttpCode() !== null && $this->getHttpCode() === $this::NOT_FOUND) {
+        if ($this->getHttpCode() !== null && $this->getHttpCode() === static::NOT_FOUND) {
             return false;
         }