Was fixing my rear washer that had popped off today, to get at the pipes that had popped off, I unscrewed the airbox and unclicked the MAF. Fixed the pipe, put everything back together, drove down the road but the brakes were rock solid and I had to work hard on them to bring the car to a stop.....accelerated and braked a few more times and now they're back to normal.

I'm just worried because I see from reading this thread that the pipe is beside the ABS unit.

I did start the car without the MAF connected, could that have caused the brakes to act strange?

I would check you haven't disturbed the vacuum line from the tandem pump to the servo. Also check this pipe for cracks or splits.

I have VAG-COM (friend giving me back my cable tomorrow) so will run a scan and see if anything shows up.

it will be a vacuum hose, either come off or lose. I dont think vag-com will tell you anything since the braking system (apart from the ABS electronics) is not link to any diagnostic circuit.

There was a post on here about a vacuum pipe back there that are prone to failing..I'll see if I can dig it up, hang on.

Here,

http://briskoda.net/fabia-i/brake-failure-question/152161/

A pic at the bottom shows a gaffa tape repair to the offending pipe, it's right next to the air box and you may have disturbed it.