I always buy my frames from eBay, then send them (along with my prescription to reglazemyglasses.com.
It's all free post, tend to get them back within 6 days.
As an example, I have rimless single lens with uv filter and anti glare coating, which cost £39.
Nothing is too much trouble, I asked for the last pair to have 2mm added to the width on each lens and that was done free of charge.
In all, my rimless Ray Bans cost me £54 (£15 off eBay). In Vision Express the total cost would have been £220.