When you have identified some prospective builders we would recommend the following steps:

1. 1. Estimates - Ask two or three builders for estimates in writing. Ask them to confirm whether there is any design or planning permission or building regulation requirement for the work.
2. 2. References - Ask each builder for two or three references. Contact the referees and find out if the staff were courteous, informative, friendly and how happy they are with the work done. If possible go and view some of the work. 
3. 3. Agree the work - Make an agreement or contract in writing. It should outline the work to be done, expected date of completion, security and safety, catering and lavatory arrangements, disposal of waste materials, hours of working and so on.
4. 4. Insurance - Ask to see the builder's public liability insurance certificate and whether they have full contracts insurance. Also, the building work may affect your home & contents insurance - contact your own insurance company to inform them of the intended work.
5. 5. Deposits and Payment - Deposits are usually only payable where specific or custom-made materials are required or where the project will take a long time for completion. Otherwise, avoid paying deposits and make sure your builder puts the payment terms in writing. On larger jobs stage payment would be expected throughout the contract.
6. 6. Sub-Contract Labour - The builder may use sub-contract labour for certain aspects of the work if this is the case, does the builder have the relevant managers in place to organise these other trades?
7. 7. Beware the VAT-free 'deal' - A VAT-free 'deal' means one of two things. Either the builder does not do sufficient business each year to reach the VAT threshold or are they avoiding their legal tax liabilities. You need to ask yourself if the builder is large enough to complete the work, will they be around if any of the work requires repair and how you can have a valid contract if there is no proof of payment.