I 'm still waiting to find out if their going to phone me back to see if they will let me buy a car from them! Been waiting about 9 months now.

Who do I need to speak/write to about the Preston branch ?
we have been very successful with resolving DPF issues by using some rather unconvential methods.
No, that doesn't really do the job, in fact, several of the people we've dealt with who've had DPF lights coming on have been those that say they give their cars hell. It seems that these people use lots of throttle at low revs and over-fuel the engine thus putting loads of black smoke (unburnt fuel) through the filter and clogging it up. Therights and wrongs of fitting DPFs is something that I can't comment on but most manufacturers are having more problems than VAG.
We use some rather unconvential methods that SEAT might not approve of and have had quite good results.