Get a court order behind you first:
Step 1:
Get several quotes, from other firms, to bring the work up to the required standard.
Step 2:
Send a formal written demand to the company for the relevant sum.
Assuming that it's a limited company, the letter must be addressed to 'The Company Secretary' (and not to any named individual), using the registered address of the company (which should be on any paperwork you've got from them; otherwise you can find it here:
http://wck2.companies...ame=accessCompanyInfo )
The letter must clearly how your name and address, and the name and address of the company. It must also be dated and clearly indicate that it's a DEMAND for money, stating the sum demanded and giving the reason why the demand is being made.
Further, the letter must indicate that if the money isn't received within a specified time-frame (I suggest 28 days) you will commence legal proceedings.
Send the letter by recorded delivery, retaining a copy of the letter and proof of posting. (Use the online tracking system to note the time and date of delivery, together with who signed for it).
Step 3:
After the specified period of time, commence legal proceedings, using the Money Claim Online service:
http://www.direct.gov...aimformoney/DG_195688
Step 4:
Wait for the court case to be heard, and your Order to be granted.
Step 5:
Await payment.
Step 6:
If payment isn't forthcoming, ask the Court to enforce judgement:
http://www.businessli...791108&type=RESOURCES
Chris