this expression is allowed uk phone numbers.
the only reliable phone format is the sequence of digits used to make a call, additionally using
+
to denote the call prefix (usually 00, but this may depend on the phone system used).
if you're calling within Germany, you simply replace the country code by the trunk code (0).
any other formatting (spaces, brackets, etc.) is nothing more than a visual aid to better remember the phone number and has no effect on the the functionality.
this essentially boils down to:
(((\+|00+)49)|0)[1-9]\d+