On another forum a few people found a cheap alternative to prescription cycling glasses, it may not be for everyone but the total cost was £30. Pick up a set of sunglasses from Amazon for £10-15 (or
eBay or those myriad of hong-kong sites) just make sure they have the little myopia frame insert and then send them off to a reglazing firm for £15-20. Link is here to people discussing it:
http://triban3owners.freeforums.net/thread/4510/prescription-glasses-inserts-cost
I've still got to send mine off. My only trouble is that I'm one of the peculiar vision cases, whilst I've got full vision my right is effectively blurred and the left takes over predominately, but I do have full wide vision,
until these fancy cycling sunglasses stick their big nose buffers the length of the nose and cut off the other eye so an alternative to that with goggles would be a lot better for me too.