Re: Second-Hand Bookdealers in London?
Won't help you find archery/related content specifically, but "The Bookshop Guide - the only guide to all the UK's secondhand and antiquarian bookshops, bookrooms, and market stalls" (http://www.inprint.co.uk/thebookguide/shops/
) provides a decent starting point when out and about. For London, there are eight lists "by postal district".
It may also be worth checking out the Yellow Pages under "Books - Rare & Secondhand"; they should be available whereever you're staying or at most public libraries.
Let us know how you get on!