I'd go for the 3.0 dCi if I was towing a van and had a full family load.
Have you considered the 3.5 petrol V6 as an alternative? The fuel consumption would be poor, but you'd pay a significantly smaller amount for one.
Have seen LPG conversions of those going for under £5k a couple of times (autotrader, IIRC). Fully loaded cars with a detuned version of the Nissan 350Z engine (or so I've read) on around a 53 plate. Chip it at your peril
We've just bought
a yet-to-arrive 3.0 V6 DCi Grand Espace. And while I'm thinking about it, prior to 2005 registrations (I think ?) are Band K Road Tax (=£245/yr) and not Band L (= £425/yr), IINVMM. Same engine, same emissions, less tax