another option would be miche. if you look at withington cycles (do a search; i forget what the exact address is), and look for miche, you'll fiond what they are called. they are for freewheels.
the problem with more or less any bike repair is that it rapidly comes to cost more than the bike is worth. so to make it worthwhile, consider giong for minor upgrades rather than straight swaps. i did that with my dawes in september: all the bottom end shimano gear was knackered and got binned, and i put a sora/deore lx mix on instead
dave