My only concern about going for an older turntable is that my knowledge of them (at least for now) is so low, that I'd be worry I'd get something which needs fixing up or is beyond fixing up. How will I know what to look out for?
That's a valid point.
I think you can save yourself a lot of grief if you buy from the right type of person. There are specialist Hi-Fi forum sites such as PinkFish and Hi-Fiwigwam. They have classified sections for selling on gear as people upgrade. You're more likely to find a well looked after TT from an enthusiast site rather than taking pot luck with Ebay.
It's also worth bearing in mind that solid plinth turntables such as Pro-Jects and Regas are an extremely simple design. There's no complex suspension to set up or maintain. It's basically an MDF plinth with a bearing for the platter spindle, a motor, a power switch and the tonearm. If you're looking at a TT that seems to have had a hard life then walk away. But something where it looks fresh, there's a box and a manual is generally going to be a safer bet.
The one area that is trickier to assess is the cartridge. Unless you have a microscope and know what you're looking for then the best way to tell about the wear is to listen. A worn stylus will show up as excessive sibilance in loud vocal passages. There's good info on the topic here:
http://www.audioinvest.no/tt_vinyl/ttv_styl.htm
I guess in the end it's about weighing up the pros and cons. With a new TT you get a warranty, you're the first owner, the cartridge is new but basic. That last bit is important.
Cartridge quality varies with price and design. TT manufacturers buy in volume but you're still only looking at a very basic cartridge being supplied with an entry-level turntable. Once the novelty of owning a TT has worn off then the cartridge is usually the first target for an upgrade.
I remember my first couple of cartridge upgrades back in the mid 80's. The TT came with a budget Linn cartridge - a K5 - You can still buy the Audio Technica version (AT95e) today for under £30. Changing to an A&R C77 was a revelation. More bass weight, clearer midrange, sweeter top end. The next upgrade was to the A&R P77. Wow! Just more of everything and better all round. At that point I'd spent almost as much on the cartridge as the TT cost, but it was worth every penny.
I've had a few different TTs and cartridges since. My current cartridge will cost around £450 to replace with new.
The thing with a good used TT is that you'll often get a cartridge at way above the performance level you could afford if buying new. So that £150~£200 used TT might come with £100~£200 worth of cartridge if bought new. As long as it's in good shape then its the bargain of a century.