That's the thing... one can now get KILLER deals on used, recent FTB4s that people are selling to get a B4.1... it's not uncommon to find GBP80 cars that are pristine. Go this route and find a "reliable" used B4FT, don't bother buying it new now anymore.
I had both a b4 and b4.1 and honestly the differences between both kits are worth it, if only for the V2 shocks and rear knuckles. The rest, granted, plastic quality has dropped significantly but this is not hampering performance.
My 2cts
Paul