If you wanted to try a modern synth for little money it might be worth checking out Rob Papen's Go2 - I got it very cheap with loyalty points I had but even at £21 I would say it was a good buy.
Also second what people say about the Air synths - just make sure you get them cheap as they are almost always on offer! There's a couple of £10 packages at PlugIn Boutique at the moment. I really like Xpand2 and Hybrid & Vacuum pro are entertaining too. I suspect they may be a bit long in the tooth now but work fine for me in CbB