update
After searching I found this code in spryvalidationtextfield.js and modified it as follows
'phone_number': {
formats: {
//US phone number; 10 digits
'phone_us': {
pattern:'(000) 000-0000'
},
'phone_custom': {pattern:'(00000) 0000000'}
}
To my total lack of surprise it did not change the format to UK
Ian