Reading the original posting, have kwik-fit actually done anything wrong? If your mechanic didn't clean the drums out properly after changing the wheel cylinders, old fluid would still find it's way out of the brake mechanism, there may have still been some fluid on the outside of the drum or on the backplate-in this case the tester would be duty bound to fail it.
After all, no dimantling is allowed in the MOT test, so the tester can't see where the fluid has coming from, all he can see is some brake fluid: even if the brake is efficient enough to pass the brake test, it can also be leaking, and the tester must err on the side of safety and assume that it is. Don't forget, testers get regular unannounced visits from VOSA, and the testers job is on the line if he passes something which maybe shouldn't.
The answer is to go for an MOT is your local authority's testing centre- nearly all councils have them as they need to test their own vehicles, and I have always found them to be fair because they are not actually looking for repair work- all they do is test.