I can only give one example so I wouldn't give it too much weight as something that could be generalised across the entire BMW service network.
I bought a 2000 model 1150GS in 2001 with 10000 miles on the clock. It came with a FSH from the supplying dealer in Bristol. I had the 12k service done at the same place a few months later.
Then I moved to Cardiff and had the 18k service done at Rydales in 2002. During this service they found that one of the rear brake pistons was corroded enough to stop it being pushed back into the caliper: not a problem at the time but it would stop a new set of pads being fitted at a later date.
My bike only came with a 12 month warranty: the 2 year warranty was introduced c.2002 IIRC. So, Rydales contacted BMW to see if they would contribute to the repair cost as they had the opinion that the quality of the materials used was sub-standard. BMW came back with a 50% contribution towards the parts cost.
So, 15 months out of warranty with 18000 miles on the clock BMW contributed to the cost of repair. Arguably, they should have done this anyway as you would expect a brake caliper to last more than this time. Therefore the Sale of Goods Act section about merchantable quality could apply. However, it is my opinion that if the bike had been service outside the BMW network then I would have come up against a solid barrier of disinterest from BMW GB. There again, if I had used a non-franchised service outlet then I would have probably saved nore than the cost of a new caliper across the 12k & 18k services.