Wait for it tho...Mr "Crappy BMW's !!" will be along soon, no doubt. 
You called

The engine is capable of huge mileage, IF (and its a bloody big IF) it has been well maintained. Remember, the earlier ones had a 4.5k MAX service interval (ideally every 3k). Later ones have a 7.5k service interval, yet no changes to engine or oil, so that was purely a marketing ploy (the 4.5k service must have been too embarrassing for Vx - TD Omegas were sold to high milers, so people were having to service every 4 - 6 weeks!!). Poor oil servicing can cause massive problems (been there, done that).
The engine is also prone to very expensive repairs, which in reality are terminal.
When you view, start from cold. It should start absolutely on the button, as soon as glow plug light out. If it doesn't, walk away. If the seller does the 'that will be glow plugs mate', ask yourself why he hasn't changed them himself then.
The cooling system on these is problematic (waterpump sheds its impellor, rads silt up, stats seem to fail). It should cruise at just under midpoint on gauge. Try to give it a good hard slog from standing start to motorway speeds a couple of times in quick succession (so a good 20s on foot-to-the-floor throttle). If it goes up to anywhere near the 100 mark on the gauge, walk away.
If its an auto, any tiny glitch or anything not absolutely perfect with the gearbox, walk away.
Be aware some parts for this engine are expensive - fuel pump is about £1200. Waterpump is about £100 for genuine. Rads about £250.
Get a good one, and give it tlc (inc 3k oil changes), and it can be a good workhorse. An abused one will be a whole heap of hassle.
A chip is a good idea to get up the lacklustre performance, though if its an auto, you will need to put on the stronger AR35 gearbox first.