Dear Joolz,
If you're going to be filming a moving subject, just make sure there isn't shutter delay, which is quite common on cheaper cameras, especially the Fuji's. Basically this means that as you see the subject and then press the button, it can be upto a second before the camera actually takes the picture, which is obviously a pain in the arse when filming, say, a racing car or aeroplane moving at speed.
I bought an Olympus E500 for £250 off of ebay, brand new from hong Kong and is a wonderful entry level DSLR with interchangable lenses.
Hope this helps.
Kindest,
Vic