Na, should be ok....there will now follow lots of threads about alarm and code failures after disconnectin g the power
Seriously, I've had my battery off loads of times with no problems at all (prob until next time!!!). If you are worried you can wire up the old battery and new one so there is no interruption in power.
You can also use those cigarette lighter power couplings from Halfords, they connect between 2 car cig lighters and maintain power to radio, ECU etc. No need to prat about with jump leads to maintain connections then.