Download the form from here:
http://www.diplomatie.gouv.fr/fr/IMG/pdf/visag b.pdf
If you live in Cheshire, Cleveland, Cornwall, Cumbria, Derbyshire, Devon, Durham, Greater Manchester, Tyne & Wear, Isle of Wight, Lancashire, Merseyside, Northern Ireland, Northumberland, Shrophire, Staffordshire, Yorkshire or in Wales, you can apply by post to the London consulate.
If you live in Scotland, you can apply by post to the Ediburgh consulate.
Note that postal applications take several weeks to process. If you require a faster service, or if you live in a part of the UK not listed above, you'll have to attend an interview at the London consulate.
The fee is the sterling equivalent of €60 (roughly �40). For further information, start here:
http://www.consulfrance-londres.org/article.ph p3?id_article=326
Chris
PS: The visa issued will be a 'Schengen visa', which permits travel across a group of 15 countries, not just France.