Maybe buying a G280, or it could be for sale

Hello most informative and useful website.
I am in the slightly odd situation of either buying a neighbour's G280LWB or, if the price is too high, selling it. The thing is, I have no idea what it's worth. I am keen to get the best price for my neighbour and you folk seem to know more than most about how much they change hands for.
I could, of course, simply tell her that I asked and everyone said it was worth two hundred quid and she'd probably believe me, but I can't quite bring myself to be so rotten despite rather liking the car.
Obviously it's not straightforward because this car will fail its next MoT thanks to a blowing exhaust and leaking seam on the petrol tank, plus whatever else crops up on a 1989 car. I would guess, having looked at posts, that an exhaust costs about £400 and the tank can be sealed for about £60 plus a fixing kit, whatever that costs.
If I describe the vehicle could someone give me a ballpark figure? I have no pictures but you people seem to know what they look like.
It's a metallic red/burgundy 280LWB auto, 1989, pretty basic spec. Body seems to be in very good condition with little rust. Needs two new tyres. Serviced at Lancasters all its life until three years ago, since when it's basically sat off the road and been serviced and MoTed annually. 117,000 miles, driver's seat a bit worn, odd ding on the bumpers, does about 15mpg, more comfortable than a Discovery, towbar, light protectors, front and rear diff locks but don't they all have those? er, that's it.
I've used it a bit and do like the car, and have persuaded my wife that it's a great idea. So tell me it's worth £200 and I'm laughing.