Strange brake problem (B5.5)

[vwscooby]

Ive had a problem with a binding NSF caliper for a little while but all of a sudden all four corners are binding on solid.

Its got so bad the car will only do 30mph flat out at 12mpg!!!!!

Had servo checked, no problems there. All four calipers have been off and had new seals and been copper greased. Had all new flexi pipes, pads and discs and the problem is still there.

Now here is the odd part. Pull away and it will drive perfectly for about 3 miles until the brakes stick on, pull over turn it off and wait 10 mins and they free off, until you travel another 3 miles then they stick on again!

Ive been to 4 garages and spent 500 quid trying to get it sorted and its doing my head in!!! Ive asked garages to check the master cylinder but they keep telling me its not that but what else could it be??!!

At the moment the car has been sat in my works car park while the T&T ran out and I feel a bit sorry for it!

Any advice???