Start with www.grayandosbourn.co.uk (08702 411166), a website that looks after size 10-20 and has a comprehensive collection of special occasion wear. Alternatively, Frank Usher's Quintesse Collection (sizes 16-26) would be great for you. And don't forget to have a look around the Plus departments at Harrods, Knightsbridge, SW1 (020 7730 1234), Selfridges, Oxford Street, W1, (08708 377 377)

I've heard good things about Marina Rinaldi too in Old Bond Street (020 7629 4454) - part of the MaxMara empire and serving sizes 14-26.