The moral of this story is always checkup on these companies BEFORE parting with money. 5 seconds on Google and I have found that caughtion is needed with this firm. If I were you James I would contact you CAB - Trading standards - BBC Watchdog.
What ever you do don't pay them any more cash!
Take them to the small claims court??
There is a similar firm being investigated today in the Daily Mirror. It seems to be an easy way to con people. They (the Dialy Mirror) actually advertised a motor bike in the small ads which the model quoted doesn't actually exist, yet got a call from these people saying that they had buyers and had recently sold a similar one for more money.