Thanks for all the responses everyone.
I tried my mums' sim card in my phone (she's on a different network) and it worked, so I guess that means that I'm in luck and my phone is unlocked, so I should be able to use it while I'm abroad and just buy a local sim with calls and data.
My company wont let me suspend my contract and there's no one that I know who could take over my contract either. Cancelling my contract is pointless as it looks like it would cost almost as much as keeping it going.
At least keeping it gives me something to use when I'm back in the UK for the odd week or two which is helpful I guess.
I've started looking around to get an idea of prices and it doesn't seem to be too bad. I'm not sure how busy I'm going to be with settling in and finding my way around so I may have to put up with the charges from my UK company for the first couple of days although, from what I've been reading, it might be possible for me to buy a sim when I arrive at the airport in Germany? Having never stepped foot in an airport in my life I wouldn't know if that's true or not.