Although I usually used F & B at Sandbach (calling in on or returning from a trip to Wales) I have used Brookside Garage on occasion at Sabden. They were recommended to me by a site member and they did a good, professional job without any marks on the rims. They are more expensive than F & B but you'd lose that gain if you made a special trip to Sandbach.
Cost of tyres obviously depends on what you have put on. The last time I was at F & B I had a pair of PR4s fitted to my Triumph Explorer (same size as the GS). The ride in, ride out cost was £232 but I also qualified for a £35 rebate from Michelin that they were running at the time meaning a net cost of £197.
Once when I needed a 'quick change' I took my Explorer to Jennings Race Motorcycles at Oswaldtwistle and my rear wheel was very badly marked. In their defence, they did offer to repaint it.
Mike