First of all I'd like to thank evryone for the most excellent, thought provoking advice. I've taken it on board (I think!) and had another look around so secondly, please can I get your thoughts as far as value for money and any gotchas to watch out for on this age/mileage/model for sale from a used car dealer?
2005 55 Reg BMW 330d M Sport (registered Dec 05)
Price: £16,999.
40k miles
Silver metallic paint
Manual, 4 doors
Sat Nav, black full leather, BMW Connect Drive Assist, Bluetooth, ipod aux connector, parking sensors, sports seats, rain sensor, 18" alloys.
Supposed to be in very good condition with FSH. Has had two owners, bought by dealer from a leasing company.
Comes with an RAC Inspection (I don't know how thorough these are) and HPI report, mileage guarantee and moneyback guarantee (if mileage or HPI turns out to be duff).
The spec looks perfect, more than I could have hoped for. My only concern is fuel consumption. If this would do anything near 40mpg on long m-way journeys I'd be happy with that - but surprised, considering it's a 3.0L.