Just off to pick my new one up today. Paid bit less than half what you did, but then it is older with more miles and a private sale. They are good motors though, and the few known faults (if they occur) are pretty easy to rectify.
The UK Passats forum is indeed very helpful. In the B5/B5.5 section, there are a load of stickied threads all about what to look out for, and how to fix the few known issues that can occur.
The biggest problem (and if not fixed it can cause a multitude of woes, but fortunately it's a very easy fix) is blocked drains in the bulkhead. There's a how to on the forum, but basically leaves and mulch block up the drain below the battery in the bulkhead, and once it floods (damp carpets in the front footwells are a giveaway) it can take out various ECU's controlling things like the ABS and alarm etc. To fix it, it really is as simple as removing a cover to access the battery, removing the battery, and cleaning all the crap out and unblocking the drain hole before putting it all back together. Takes about 1/2 an hour, probably needs doing once every few years, but it can cause a multitude of issues if not done.
They really are pretty solid cars if looked after well. Just MAKE SURE that if the cambelt was done recently, they changed the tensioners too. If they didn't, insist they take it back to do the job properly. I have been victim to a bodged cambelt job in the past sadly, bought a car with a very recent cambelt change and within 3,000 miles the belt slipped a tooth, valves hit pistons, and my engine was toast!
Sadly, I had no comeback at all because the garage that did the work (a VW main stealer no less, a good independent is 100 times better than a main stealer IMO) only warranted the work for the previous owner, despite it falling well within the 12 months and limited milage period covered by their supposed warranty.