Thanks Dave, actually I found the mixer dimensions and weight specs. Like you said, the Behringer is lighter but the Soundcraft is smaller so it's swings and roundabouts really. The Soundcraft seems like better quality to me too, but the Behringer would still do the job at the end of the day.
Behringer = Weight 5.09 kg, Width 430mm, Length 355mm, Height 90mm
Soundcraft = Weight 5.66 kg, Width 380mm, Length 388mm, Height 113mm
Like Chili says, I should just pick one and get on with it. I won't need it until our March practice as this month we're just going to practice without the mics. Either of them will do the job so that's all good. There is however one final piece of the puzzle to get once I've got the mixer. I need some sort of bag or case for it, to carry it, its power supply, the 7 drum mic XLR leads, and the two 20ft Mixer-PA XLR leads. Obviously I need to get the mixer first to get a case the right size! Hopefully such a thing exists! I could just chuck it all in a shopping bag or random hold all but I prefer to have things a bit protected in transport when I've spent loads of money on it.
The mics (Shure drum mic set) come in a convenient carry case which keeps them all safe and together. Having the rest of it just chucked in a random bag seems like a bad move!