I've had my VR6 for six months now since upgrading from a mk3 16v, i've covered about 8k miles in it.
Fuel consumption from mine is 26mpg according to the long term trip computer, which seems accurate when i've worked it out using petrol and mileage. Most of my driving is on A roads, hardly Motorway at all and a fair bit of town traffic. I drive fairly enthusiastically most of the time.
Regular Oil changes are really important for a VR6, every 5,000 miles is necessary, it takes 6 litres of oil and a vw filter is a complete rip off at ?12.
Main Dealer servicing is about ?100 for oil change, ?170 for Inspection 1 service and ?280 for Inspection 2. Services are every 10,000 miles. And obviously cheaper at independants.
Mine had new tyres on when i bought it and i reckon there's at least another 2,000 miles to go. And they are cheap crap tyres! So it's not too bad, most people reckon 10,000 from a pair of fronts.
There are not many known faults. Early VR6s did have head gasket problems but it is fairly rare, later ones were changed for a better part.
The main thing to go is the cam chain tensioner and guide rail. The tensioner on pre 97 vr6s is poo and doesn't work very well leading to a broken guide rail and possibly even chain damage. This usually starts showing at about 100k miles and you can tell by a very rattly engine between 1,000 and 3,000 rpm. When its bad it sounds like a sewing machine. Replacing the tensioner and rail is quite easy i understand, Probably costs about ?300 at a garage. It can be changed for the new style part that works much better and lasts a lot longer.
Insurance is a lottery, but with you're ncb shouldn't be too scary, get some quotes! Vr6s are group 16-17.
4k should get you a very nice VR6.