[Thompy]

Hey guys, first of all apologies about the no classic content, but I'm a bit stuck (literally)
My car is a C5 A6 2.7Tq
Went out this afternoon to take some boxes to the local recycling centre. About a quarter of a mile from the recycling centre I pressed the brakes, found the pedal hard and the brakes seemed to be binding (not releasing when I released brake pedal). The binding got worse and by the time we got to the recycling centre the car was really straining against the brakes. Emptied the car and decided to try to get home, when I tried to set off the brakes seemed to be solidly on and the brake pedal was rock solid. I tried a couple of things - disconnected the vacuum hose to the servo and pulled the plug on the ABS pump. Neither had any immediate effect, but after about half an hour, once the car and brakes had cooled there didn't seem to be the same degree of binding. So we set off for home, only to feel the brakes starting to pull again after about 1/4 mile. Same thing again, after a period of time we could move and get a bit further up the road. I didn't have any tools with me, no breakdown cover and no phone a friend available, so we made it home in this fashion about 2 hours later (luckily we were only about a mile from home). I'm thinking it may be a problem with the master cylinder, since disconnecting the vacuum to the servo had no effect and the chances of both front callipers sticking at the same time is unlikely. I've had the car jacked up and there's nothing obvious wrong.
So what I'm asking is do you reckon it's the master cylinder, if so is it reasonably easy to remove/replace (I'm fairly handy with a set of spanners and generally tackle most things myself) and finally do you guys have any other suggestions before I start into a process of elimination.

Bit of a wordy one here but I've tried to give as much info as possible.
Thanks in advance

Andrew.