Hi Martin,
A mini-lathe might do what you want: they'll do steel so aluminium and brass are no problem. I see Warco's latest version of the mini-lathe comes with a brushless motor which is a useful improvement.
A mini-lathe is an easy two person lift, and you might be fit enough to lift one on your own. They don't take up much room. On the downside the maximum size you can turn is about 100mm wide by 300mm long. The hole in the spindle is 20mm, if for example, you wanted to put a thread on the end of a barrel.
Next up and nearly within your budget is the WM180: the main advantage is that it's bigger. One of the best bits of advice I've had off the forum is that bigger is better when it comes to lathes. Partly because people tend to gravitate to towards turning bigger objects, partly because the extra space makes it easier to work on stuff.
The WM150 is new to me.
I've had nothing but positive experiences buying from Warco. I've not tried Chester and can't comment from personal experience. You might like to search the forum to see what others say though.
If you get the chance to look at one before spending hard earned cash it's well worth it. I happened on a mini-lathe on display in my local MachineMart. I didn't buy one off them but seeing it in the flesh confirmed that the type would do most of what I wanted.
Dave