Did you get the name of the Contractor?
If so claim against them here:
www.moneyclaim.gov.uk/
I've claimed from a company before and it really does work. If the defendant does not respond within 30 days of your claim the Court will judge in your favour and instruct the defendant to pay you within 30 days. If they fail to pay they send the baillifs in, which happened in my case and I got my claim paid - no questions asked!