A Zoom GFX1 unit, for around £60, great for gigging and pretty decent effect patches for it's price, even better; if you own a foot controller, you can attach it to it for full control of the effects, and then you're laughing.
the zoom g.2, brilliant for the price, u could get the one with the expression pedal for jus 10 quid over budget, but the standard g.2 is amazing as it is anyways, so if your budget is tight, then thats the best one.
I dunno... Maybe I'm wrong but Zoom seems to be ****. The sounds quality sucks. But then again, I don't know anything better at your budget. Maybe something from Boss?
for rent
Zoom G2. I've got mine set-up better than a friends POD ( 2 I think ) and another friends Boss ME-50. They've both been playing guitar longer than I have too. Get one with an expression pedal if that's your thing.

My only complaint would be the wah, but I haven't played a wah that I'm happy with, and don't use wah anyways.
Fight the urge to buy a multi-effect pedal. I haven't heard one I liked yet. Too much knob twisting for my taste. I'd sooner plug my guitar directly into the back of my computer and use it as a midi controller for a software synth or modeling program.