For the Spry validation, if you wanted the phone field to be entered in that exact format, you would select 'custom' from the Spry options in the properties panel, and in the 'Pattern' field you would put: (00000) 000000
You would also show this pattern in the 'Hint' field by typing in something like (01234) 123456 because I think few people would think to do it in that format.
Other custom options for UK format to put in the Pattern and Hint boxes could be 00000 000000 or 00000-000000
If you are also using WA Server Validation to validate this field, select Validation type Phone Number, and tick the box 'Allow international' - this allows for all phone number variations.
I tend to make the Spry just validate as 'Required' (with 'None' selected as Type) and then use the WA Server vlidation as Phone Number with 'Allow International'. This seems to cover all situations.