£3700 is a good price for that spec. I just paid 6800 for a late 06 one with FSH & 90k on the clock in very good nick, after shopping around quite a bit and thought that was an OK price. We were sold on the mega sunroof really.
If I'd seen the one you have in mind I'd probably have taken it - there's zero benefit in buying from dealers these days when you can do your own HPI check & buy your own warranty etc.
Maybe things really are cheaper up north ;-)
We have a Warranty Direct policy on the car for main dealers, costs £500/year.
Tax is a b-arch on these, being the highest band. £450
140 vs. 180BHP? I haven't read much overall (yes, factoring in the advice from d'Espacebetweenmyhears hereabouts) to say that the smaller engines last any longer - have rung 4 Renault dealers and spoken to head mechanics who said much the same. A solid FSH and no overly-visible smoke is about all you can do, barring getting a mechanic to check it over as well.
We are only really using if for holidays when it will be fully loaded (450L roofbox, 5-6 people + Labrador, 4 bikes, trailer, big tent, sink, etc) for me drivability under heavy load is more important than about-town economy. It gets 35MPG doing 80MPH along with everyone else, which isn't bad for a 1900kg garden shed on wheels.
And of course watching the Youtube crashtests of Espace's is always peace of mind.