These are a few sites that you may find useful

Fensa The industry standard for replacement windows and doors

Building regulations

Trade Organisations Bodies

British Cement Association (BCA)

British Precast Concrete Federation (BPCF)

Builders Merchants Federation (BMF)

Chartered Institute of Building (CIOB)

Concrete Society

Confederation of British Industry (CBI)

Copper Development Association (CDA)

Federation Of Master Builders (FMB)

Institute of Roofing (IOR)

Lead Development Association

Lead Sheet Association

National Federation of Builders (NFB)

National Federation Of Roofing Contractors (NFRC)

Timber Research and Development Association