Where do I find the fuse box?

We bought our first caravan in August - a 2003 Abbey Freestyle 520 SE 4 berth and I would like to ask experienced caravanners for help of where we can find the fuse box. The fan on the heater isn't working and we think it may be just a fuse which needs changing, but cannot locate it! The handbook isn't giving us a clue, and even phoning Abbey(Swift) direct could not tell us! Many thanks, Di