Here are links which you may find useful. The following are personally recommended:

The Singing School - www.thesingingschoolbushey.co.uk

The Gray Singers - Our Concert Troupe! www.thegraysingers.co.uk

Harrow Philharmonic Choir - www.harrowphil.co.uk

London Oriana Choir - www.londonoriana.com

Potters Bar Choral Society - http://www.pbchoral.org

Harrow Opera - http://www.harrowopera.co.uk

Dee @ Style Photographics - Wedding Photographer - www.stylephotographics.co.uk