Addition of en_GB mobileNumber methods

src/Faker/Provider/en_GB/PhoneNumber.php

@@ -16,4 +16,24 @@ class PhoneNumber extends \Faker\Provider\PhoneNumber
         '(0####) ######',
         '(0####) #####',
     );
+
+    /**
+     * An array of en_GB mobile (cell) phone number formats
+     * @var array
+     */
+    protected static $mobileFormats = array(
+      // Local
+      '07#########',
+      '07### ######',
+      '07### ### ###'
+    );
+
+    /**
+     * Return a en_GB mobile phone number
+     * @return string
+     */
+    public static function mobileNumber()
+    {
+        return static::numerify(static::randomElement(static::$mobileFormats));
+    }
 }

src/Faker/Provider/en_NZ/PhoneNumber.php

@@ -77,15 +77,6 @@ public static function mobileNumber()
         return static::numerify(static::randomElement(static::$mobileFormats));
     }
 
-    /**
-     * Return a en_NZ cell (mobile) phone number
-     * @return string
-     */
-    public static function cellNumber()
-    {
-        return static::mobileNumber();
-    }
-
     /**
      * Return a en_NZ toll free phone number
      * @return string