I think I've fixed my problem. When i was turning the screen on from standby I kept noticing the 3G/H icon in use - now I only have 2 sync accounts, gmail and the inbuilt exchange which is linked to my hotmail.
Browsing through the data usage graph, I realised that the exchange service was using approx 600k-1mb per day in data. Except for the last 3 days in which it has used 12mb, 15mb and 19mb. Constant drip of data coming in = battery drain.
Disabled sync for that one account, went out for an hour and the battery dropped only 1%. Now to try and work out WHY it's doing this. I've not changed any options, its set to 3 days worth of synced emails only, push email and nothing I can see would explain why it is burning through 20x the data it should each day.