BriMarsh: If your that bothered about money don't buy something so overpriced as a Mini, and definately not a brand new one.
Ok so BMW do charge a premium for a Mini, but the actual long term ownership costs are superb. BMW have worked some clever marketing to ensure resale values are strong (Mini TLC servicing pack for example), plus the car is simply desirable which always helps.
I don't think it would take much to put the 90bhp PSA diesel into the Mini as a OneD as both the 90bhp and 110bhp are the same engines with different tuning and turbos (I think). However BMW might be put off by the performance. Whilst the 110 is good (we have it in the Clubman) I suspect the 90 may not live up to the Mini's sporty nature. I could forgive it though if the figures stacked up (less than 100g/km CO2).