If it's in good condition and full working order then I don't think that's too bad, have a look at the completed items on eBay and that should give you an idea. I think the days of picking one up in Mint- condition for £100 from a camera dealership are long gone, anything approaching unmarked condition (particularly with original box and paperwork) seems to be changing hands for over £200 these days, and quite right too, it's got to be one of the best and most advanced 35mm SLRs ever made.
I'd start with a brand new battery for it (I think Energizer or Duracell seem to be about the best) as they seem to have the usual Lithium battery habit of being 'all or nothing' and going from working to flat without much (if any) warning. Unused in the packet the battery should have a shelf-life of around 10 years though, so make sure you get fresh stock. In camera it depends on how many rolls of film you use and how much you use the IS function on lenses, etc.
I wouldn't put a film in the camera until you need to either, as I've got a suspicion that this causes more battery drain even if the camera is turned off to the 'L' position; well, more than it does when there's no film left in it. I may be wrong, but that's the impression I have from my camera but it
could just be my imagination!
Blimey, at least Dick Turpin had the decency to wear a mask!
That has to be the haggle of the century, in working condition the film door alone has to be worth about twice the original asking price!