This is another trade association for plumbers and heating contractors. They offer their plumbers insurance services, training and help on legal changes/issues. They have a consumer section and also find a plumber section. You wont always find a plumber near your postcode, so try it, but then put in the town you are in if you get zero results.

Contact them:
Web:   http://www.competentpersonsscheme.co.uk/
Email:  info@aphc.co.uk
Tel:     024 7647 0626