Robsom Racing 01789 450822, Stratford upon Avon or Central Wheels at Coleshill, Both good on price with motorcycle specific machinery(no rim Damage), Ride in ride out, sameday.
There's a ProTyre in Glos that is very good, and have a drive in drive out service. I know that Gloucester is a bit more than 50 miles from you, but they have places all over the country, there mite be one near you.