TegTypeR:Unfortunately I don't think the car is desirable enough to warrant the high price tag no matter how good the engine is.
I believe from reviews of the engine in other Subarus it's not that good to begin with. So why it would be any more desirable in an Impreza I really don't know.
I find it difficult to figure out who would want to buy this. It's not quick enough to tempt anybody who would be a WRX buyer, nor economical enough to tempt you away from, for example, a 2l Golf diesel. The Golf is a better place to be in, and only lacks the 4WD system that in such a car you would have difficulty justifying (although my old WRX PPP was superb with it - but it was sub 5s 0-60!). And the Golf is cheaper too.
Alternatives to look at:
BMW 1 Series 118d, 5dr, £ 19,940.
Audi A3 Sportback 2l TDI 170, £ 20,310.
VW Golf 2l TDI 140 SE, £ 19,200.
I did have a look for a Ford Focus 2l TDCi 136 Zetec S 5dr to add to this list, but the equivalent was £ 20,695 and that's just madness!!! However, as we all know you can buy Fords cheaper than this even from main dealers.