The syntax for regular expressions on client and server are a little different. In the server field I think you need to encapsulate it with slashes like:
/(\+44\s?7\d{3}|\(?07\d{3}\)?)\s?\d{3}\s?\d{3}|\(?\d{3}\)?\s?\d{3}[\-]?\d{4}/
I'd use the original phone validation for the server. Your client validation is working, but it is very specific and without the auto-formatting it might be difficult for people to enter the correct value.
For instance if they enter a US phone number they would need to type: (222) 333-4444
If any spaces, dashes or parenthesis are missing it wouldn't pass.
A better regular expression might be:
(\+44\s?7\d{3}|\(?07\d{3}\)?)\s?\d{3}\s?\d{3}|\(?\d{3}\)?\s?\d{3}[\-]?\d{4}
That would at least allow them to omit the parenthesis, dash, and space
