Just my opinion, but separates are the way to go for the following reason:
If you're worried about having to be loud enough for lots of different venues and perhaps not having pa support etc, I'd recommend a 4x10 cab. Pretty much get away with anything with one of those as long as its driven correctly.
However, in time you might not need to lug a 4x10 around, so perhaps a 2x10 or a 1x12 etc would be better suited (or even better suited to certain venues leaving the 4x10 for the bigger ones).
With that in mind, and to save you buying another new combo, I'd spend the majority of the budget on a top quality, powerful amp head, and the rest on second hand cabs (or even one cab to start with) and see what works for you.
Head wise it depends what you really like. Loads of eq and functions and buttons? Or simpler the better? Lightweight? Built in fx? The worlds your oyster.
Theres lots of ashdown abm combos around for around £200, if you wanted a combi, but I'm not sure if they'll be loud enough. I had an abm2 500 (1x15) and it wasnt enough for me. I also wouldnt recommend a 4x10 combo - very heavy.
My main rig (and pretty much rig for everything) is a quilter 800 and laney n410. Total weight around 22kg and loud and good enough for any gig.