[Mr Gazza]

You're getting somewhere now.

If it is warped discs then it will show up on the brake testing rolling road and you will probably get an MOT fail!

More often than not it is what is known (so I am told) as surface conditioning.
This means that you could have slippy and grippy areas on the disc(s). Often caused by a patch of damp under the pads, making a patch of slight rust or vice versa if the rest of the disc is damp and the pad keeps a patch dry.

I have found that the solution to this is a severe spanking followed by a good hard lever tugging session.

By which I mean; getting to a healthy cruising speed then very progressively give a long hard brake application, as long and hard as you can. DO NOT come to a stop or let the brake off suddenly. Gently let the brake off and accelerate away immediately to repeat the exercise, ad nauseum. Please try and do this safely on a long straight empty road... Check your mirrors!

That has always worked for me, although I have also had actual warped discs (all three!) You need a dial gauge to establish that they are warped.

If they are warped the spank and tug exercise will just get more violent as they get hotter!

I just thought I would say that you need to make your own decision about acting on the advice of someone on the internet, or a bloke down the pub for that matter..