9 time out of ten the bias valve isn't seized but the pivot for the operating arm is. As for MOTs I go to a place that only does exhausts, tyres and basic servicing. They're not into fixing MOT failures, mine could have failed on play on a rear wheel bearing but he just noted it on a bit of paper!
Most of the bits you've got can be sorted easily but from experience once those rear calipers go stiff replacement is the only answer longer term.
Rejoice in the fact you have a VW, I've spent many a weekend chasing holes with a welder come MOT time in the past

Barkstar
