I've been doing archery for about fifteen years now, and I'll echo what any other archer will tell you. Archery can be as expensive as you want it to be, within reason, of course. I currently shoot a replica of a Roman legionary bow and make my own arrows, which is nowhere near as hard as it sounds.
There are several disciplines of archery to choose from. There's the well know target archery, where the archery shoots at a butt set at a determined range, or there's the lesser known field archery where you shoot at targets in the woods that are set at varying distances. I prefer and shoot in the latter discipline, though you tend to lose more arrows in field archery.
In terms of cost. If you're serious and want to buy your own kit that's not going to fall apart after five minutes, you're going to have to spend around £100. That will buy you a kit that usually includes a bow, six carbon-steel arrows etc... A good kit will last you for a long time - 10 to 15 years if you look after it. Club membership varies, but on average it'll be along the lines of £20 a year. But to become a member you'll have join the body that governs your chosen discipline. I'm a member of the NFAS (National Field Archery Society), and a year's membership £20.
But before you spend any money, book an introductionary lesson with a club like Bromley Archery (that's the one you mentioned on Whitefoot Lane), kit hire will be included in the price. If you like it, then book a few more lessons before making any sort of financial commitment. I started out with these lot, but was lucky enough to find-out about the lesser known discipline of field archery.
For further info on equipment prices, here's the link to the company I order from:
http://www.merlinarcherycentre.co.uk/
. After a somewhat fruitless few hours of searching, I was wondering if anyone had any recommendations? 