I'm a great fan of these cars (2.3/2.5-16s) but as Neil says, they don't normally make financial sense at this level. They can guzzle up money at an alarming rate, so a full-blown restoration could cost you thousands - madness when you can still find nice examples for sensible money still. Even bodywork/interiors aside, unlike regular W201s many of the parts are unique to these models and can be quite expensive.
For example - some parts prices from memory:
Exhaust manifold - £1100 + vat
Exhaust system - about £1k from MB
Rear struts - about £300 each
2.3-16 timing chain/tensioner and rails/sprockets - £1k
VDO stopwatch - £300
Having said that, for the cash that Pistonheads car looks like a bargain. It could still sting you for a good few grand though if you were to bring it up to scratch.
A bit like many older/collectable MBs - eg 126 SECs, R107 SLs etc. The difference between a rotten basket case and a peach is huge.
Even my old 2.5-16 Auto that I sold a few months ago had about £14,000 worth of bills covering maintenance/repairs for the last 10 or so years.
Unfortunately, that's why so many of these cars end up as restoration projects. People drive them into the ground because they can afford to buy them, but don't want to/can't afford to look after them.
In a nutshell - you either pay upfront or you pay in the long run, no real shortcuts
Will