diff --git a/playwright-local/tests/update/formValidation.spec.js b/playwright-local/tests/update/formValidation.spec.js
index 10dcc1b4..cc0219ef 100644
--- a/playwright-local/tests/update/formValidation.spec.js
+++ b/playwright-local/tests/update/formValidation.spec.js
@@ -1,6 +1,8 @@
 // @ts-check
 const { test, expect } = require('@playwright/test');
 const { Commands } = require('../utils/commands');
+const Chance = require('chance');
+const chance = new Chance();
 
 const email = `giftaid-staging-${Date.now().toString()}@email.sls.comicrelief.com`;
 
@@ -177,7 +179,14 @@ test.describe('Giftaid update form validation', () => {
 
   test('Validate mobile number field', async ({ page }) => {
     const commands = new Commands(page);
-
+    // List of allowed prefixes for UK mobile numbers
+    const prefixes = ['074', '075', '077', '078', '079'];
+    // Randomly select one prefix from the list
+    const prefix = chance.pickone(prefixes);
+    // Generate the remaining 8 digits randomly
+    const mobile = `${prefix}${chance.string({ pool: '0123456789', length: 8 })}`;
+    console.log('mobile number generated', mobile);
+    
     // Test cases for various mobile number validations
     const mobileTestCases = [
       { input: '0712345678', error: 'Please enter a valid mobile phone number - it must be the same number associated with your donation.' },
@@ -195,7 +204,7 @@ test.describe('Giftaid update form validation', () => {
     // Validate correct mobile number
     await page.locator('#field-input--mobile').fill(''); // Ensure the field is cleared before filling with valid data
 
-    await commands.populateUpdateFormFields(page);
+    await commands.populateUpdateFormFields(page, { mobile: mobile });
 
     // Select yes for giftaid declaration to complete the form
     await page.locator('#giftAidClaimChoice>div:nth-child(2)>label').click();
diff --git a/playwright-local/tests/utils/commands.js b/playwright-local/tests/utils/commands.js
index 516111e3..bd570c92 100644
--- a/playwright-local/tests/utils/commands.js
+++ b/playwright-local/tests/utils/commands.js
@@ -62,7 +62,7 @@ class Commands {
     address2 = chance.street(),
     address3 = 'test address 3',
     town = chance.city(),
-    mobile = chance.phone({ country: 'uk', mobile: true }).replace(/\s/g, ''), // Remove spaces from the phone number
+    mobile = '07516144519'
   } = {}) {
     await page.locator('input#field-input--firstname').fill(firstName);
     await page.locator('input#field-input--lastname').fill(lastName);
diff --git a/playwright-staging/tests/update/formValidation.spec.js b/playwright-staging/tests/update/formValidation.spec.js
index d6520009..0772b653 100644
--- a/playwright-staging/tests/update/formValidation.spec.js
+++ b/playwright-staging/tests/update/formValidation.spec.js
@@ -98,8 +98,15 @@ test.describe('Giftaid Update form validation @sanity @nightly-sanity', () => {
     await page.close();
   });
   
-  test.only('Validate mobile number field on giftaid update form', async ({ page }) => {
+  test('Validate mobile number field on giftaid update form', async ({ page }) => {
     const commands = new Commands(page);
+    // List of allowed prefixes for UK mobile numbers
+    const prefixes = ['074', '075', '077', '078', '079'];
+    // Randomly select one prefix from the list
+    const prefix = chance.pickone(prefixes);
+    // Generate the remaining 8 digits randomly
+    const mobile = `${prefix}${chance.string({ pool: '0123456789', length: 8 })}`;
+    console.log('mobile number generated', mobile);
     
     // Test cases for various mobile number validations
     const mobileTestCases = [
@@ -118,7 +125,7 @@ test.describe('Giftaid Update form validation @sanity @nightly-sanity', () => {
     // Validate correct mobile number
     await page.locator('#field-input--mobile').fill(''); // Ensure the field is cleared and filled with valid data
     await page.locator('.form__radio input[type="radio"][value="call centre"]').click();
-    await commands.populateUpdateFormFields(page, { mobile: '07123456789' });
+    await commands.populateUpdateFormFields(page, { mobile: mobile });
     await page.click('#giftAidClaimChoice>div:nth-child(2)>label'); // Select yes for declaration
     await page.click('button[type=submit]'); // Submit the form
   
diff --git a/playwright-staging/tests/utils/commands.js b/playwright-staging/tests/utils/commands.js
index 08ef6bf7..49fd8043 100644
--- a/playwright-staging/tests/utils/commands.js
+++ b/playwright-staging/tests/utils/commands.js
@@ -57,7 +57,7 @@ class Commands {
     firstName = 'test',
     lastName = chance.last(),
     email = `giftaid-update-staging-${chance.email()}`,
-    mobile = '07123456789',
+    mobile = '07516144519',
     postcode = chance.postcode(),
     address1 = chance.address(),
     address2 = chance.street(),
diff --git a/src/pages/GiftAid/UpdateForm/UpdateFormFields.js b/src/pages/GiftAid/UpdateForm/UpdateFormFields.js
index 858fb84d..99e1f5b0 100644
--- a/src/pages/GiftAid/UpdateForm/UpdateFormFields.js
+++ b/src/pages/GiftAid/UpdateForm/UpdateFormFields.js
@@ -86,7 +86,7 @@ export const updateFormFields = {
     placeholder: 'In the format 07123456789',
     label: 'Mobile number',
     required: false,
-    pattern: '^07[0-9]{9}$', // Matches the validation in the main 'submit' form
+    pattern: '^(?:(?:00)?44|0)7(?:[457-9]\\d{2}|624)\\d{6}$', // As per Update.action.js in serverless-giftaid
     helpText: 'Enter the one associated with your donation',
     emptyFieldErrorText: 'Please fill in your mobile number',
     invalidErrorText: 'Please enter a valid mobile phone number - it must be the same number associated with your donation.',