I have found the following places to place a free advert.
1/ Your local newspaper under "local clubs"
2/ Your local Council, again under Local Club Listings. Most Councils carry a list of their local clubs for free.
3 Badminton England. Make sure your club is listed.
4/ There are several "free" club listing online. Type in "club listings" (and don't forget to put "UK" after otherwise you will cover the world)in your search engine and you will find several "listings2 for clubs. Under Badminton, list yours.
www.sports-club.net is one, sponsored by Direct sports.
I will look for more - stand by and call back soon