I don't post advice as such, Ken... merely my own experience. The petrol -vs- diesel question is an interesting one. I did buy Mrs. Catcher a petrol Fabia (3 cylinder, probably 1.0 MPI) and the engine lasted 200k klios and had a new (albeit quite cheap) Catalytic Convertor around 180k. I'd expect the diesel DPF to be good for 300k. In a manual diesel the clutch will probably last 150k, in the DSG 300k. In short I'm not sure that I'd consider a VAG petrol for a taxi. If you intend doing more than 300k over the maximum 10 year ownership period the diesel mightn't be the best choice either. Like I say if money was no object I'd buy the DSG diesel expecting to be finished with it within 300k kilos i.e. when it starts to get expensive to maintain. I've taken a bit of a gamble with the MKIII in opting to keep it until next year as it has c.262k on it now and a new clutch would cost €1,700... I could end up doing a bullet but then, who knows, maybe there'll be an age extension for 2016 regs in which case I wouldn't be too put out by replacing the clutch.
You can't just turn the light off, erm or just programme the auto regens out of it. You have to get the thing drilled out as well. If you don't do both it'll likely go up in flames. Also, it's illegal to drive a diesel that's been so modified... but, strangely, not illegal to modify it. In the case of the VAG DPFs they're not that expensive so you might as well replace it if you intend keeping it for any length of time after it fills up.