I thought I had a faulty ABS module which was causing some warning lights to come on, but now I'm not so sure. Symptoms are:

Brake/ABS/STC/Service lights randomly come on and stay on for anywhere between 1 minute and several hours.

When the brake light is on, the trip meter goes to "---.--" and the mileage counter stops counting! They both resume from where they left off after the brake warning light goes off.

A few times I've been gently braking (like when coming up to traffic lights) when the brake warning light came on... As soon as it does, the ABS kicks in for a few seconds! (you hear and feel it on the pedal)

And I've noticed that sometimes driving over a bump in the road, or accelerating HARD, will make the brake warning light go out if its on....

So, any ideas? The fact that the ABS kicks in when the light goes on suggests to me that maybe theres a dodgy sensor somewhere or other....? How hard is it to get access to the ABS sensors to see if they're dirty?