I use a Drummond M-Type and it's quite a nice little lathe.
This one in your picture looks like a Drummond B-Type of 1912-21 era.
Here are some pics and info, showing the change gears and possibly end of the spindle that are missing. http://www.lathes.co.uk/drummond/page5.html
Drummond gears come up on eBay UK fairly regularly for five to ten pounds each, so factor that into your equation. To do screwcutting you would need a dozen or more.
Does it have the electric motor and countershaft with pulleys on it?
Will it be a black hole for money??? It's kind of like buying an old car or motorbike, if you chance upon a good 'un with relatively little use, well looked after, all there etc etc, it can be quite good. But if the lathe's bed is worn and needs reground, cross slide ditto, headstock bearings are clapped an you have to pay a machine shop to make you some, leadscrew half nuts are clapped and need new ones makes and so on, yes it can turn into a black hole for money, and when you have spent all that money, the lathe is not worth very much.
I see M-Type Drummond/Myford lathes come up on eBay UK fairly regularly at very cheap prices, with tooling and accessories. You might be better off looking at one of them, if this one is not in very good condition. The M-Types have more features and are a greatly under-rated little lathe.
There is a Drummond owners group on Yahoo that is quite helpful on these old models. It is here http://finance.groups.yahoo.com/group/drummondlathe/