Well came out of morrisons tonight and the car started and then cut out straight away called my mate who is a VW tech and he checked the wiring and relay, all ok. The pump it seems has just had it!
The pump has been steadily getting louder and louder over the last week,it's been buzzing like when it first primes constantly as I've been driving.
im quite lucky as I work in a VW dealer with TPS next door so hopefully I can have the part in by thursday latest.
I love my S3 but these things are sent to try us!