Well, the way I look at it is if you're daft enough to buy something second hand from an auction (physical or online) (I do it a lot) then you better have a good idea what you're trying to achieve or be prepared to waste some/all of your money. Consumer protection law is all well and good (I used to advise at Citizen's Advice Bureau) but remedy isnt always easy...its more about judging who you're buying from.
The 20+ yr old bandsaw I got second hand recently is a great example...fair price, really nice guy, good machine with some minor 'medium hassle' faults, easily fixed for less than £100 and now working well.
As for the p/t I'm going to see ...I'm pretty clear what the issues probably are (blades maybe stuck in place, guard broken, replacement guard may need upgrading..but machine basically working ok). Belts, bearings, springs, grub screws etc can be replaced, wooden guards made, but in a medium-low-ish value item, the tables, spindle and the motor seem to me to be the key items to have a glance at (if they're shot then it def aint worth the money).. I imagine that's easily tested by trying it out on the sort of stuff I'm going to use it for.