I had a similar dilemma... not many seem to rate the
JCW brakes and at the price they need to work as well as be shiny and red!
Just had Spiroslots fitted yesterday at GTT and even this early they seem to have a lot more stopping ability - and that's even on my overweight
MCSC. Roland said they will get better once bedded in... can't wait. The discs also look really good even with the standard calipers. For the same money as buying JCWs you could have Spiro's all round fitted and fresh DOT5.1 fluid.
Should look after you on those back roads :-)
Roland and GTT are a class act by the way.