Account verification codes, How much of the telephone number is it prudent to show the user?

We will be asking users to generate an account verification code that will be SMSed to them in order for them to sign in (as an alternative to emailing a password reset link). How much of the (mainly UK) telephone number is it prudent to show them so they can tell it's the right one, given that they haven't yet verified it's them? I have seen this on other sites:

07*****1234