Similar topic recently discussed here -
Japanese imports - if you wish to enter into the thread.
One of the most highlighted issues on any Volvo 5 cylinder white block is the clogging up of the Positive Crankcase Ventilation system. This comes about generally due to neglect with regard to oil change intervals and incorrect spec of engine oil used. As a result of a blocked PCV system you get oil trying to push out at the seals...the rear main crankshaft seal being the most expensive to replace due to the labour involved. A simple test with a rubber glove held over the oil filler with an elastic band will determine how well the system is breathing. If it inflates you've got issues.
Also have a read of -
850, 70 And T5 Buyers Guide - courtesy of Jod_T5
Being ex Japanese my guess is that the car you're looking at will have an extensive service history, they're quite strict on emissions so tend to look after their motors, and going off the ad it's been previously NCT'd and taxed so you're good to go albeit at a premium. Going from the description they've gone to great lengths to bring the car up to Irish/UK standard. That particular ad is several months old and, if I'm not mistaken, was first entered at €10,999. I'm curious to know how much these are selling for in Japan.
Mega motors in my personal opinion, the "Golden Age" of car manufacture, but I would be quite biased in that regard