The answer lies in the small claims court - cost will be £27 but keep exact details of all telephone calls and conversations, with whom they were carried out, and copies of correspondence including e-mails.
If if gets to the small claims court stage, you will find that the judges are very friendly, helpful and very fair in their judgements.
You can do the initial claim on-line but be prepared to be brow beaten by the defendent's solicitors attempting to try and frighten you into dropping the claim.
It happened to me last year (a big London firm firm of solicitors were appointed to oppose me over a very modest claim).
But I stuck to my guns and the company's solicitors didn't even bother to be represented at the hearing, despite trying until the 11th hour to try and convince me I would almost certainly lose and would fact costs of £2,000 or more.
The judge who took the case treated the solicitors' aggressive approach with the contempt it deserved.
So the company I sued not only lost the case and had to pay up, they also had to face the cost of appointing central London solicitors....:-)
As a point of interest this particular company was also facing legal action from Ordnance Survey in the London High Court - I think it lost that one as well.
An expensive pastime if you don't have a leg to stand on...:-)