Micheldever Tyres import most of the tyres in the UK. I think their sales markup is a bit more than others, I got Bridestone SO-3 tyres for my GS from Bracknell tyre and battery for £8 less each even though Micheldever supplied them.
What Potenza's are you going to get? Don't ask for a quote for just Bridestone Potenza as this is a range of tyre, there are several models SO-3 being the top of the range.