I recently got a Colchester Student lathe and it's excellent. About £500 on eBay at the moment. As good as the Harrison M250/M300's at school as far as I can tell...plenty of options for thread cutting and the spindle bore is about 40mm, can't remember exactly but it's plenty.
It's not the easiest of things to get in your garage/shed though since it's very very heavy. Any good lathe will be very very heavy though...

I did have a Sieg C3 mini-lathe, 20mm spindle bore... I wouldn't recommend it. It's a toy compared to what I have now.