I discovered http://www.glassesdirect.co.uk/, who not only do online glasses including varifocals (like many other companies, it seems), but will actually allow you to pick up to 4 frames to receive as a 7 day “home trial”. Frames come with plain lenses, of course, but I think it’s an excellent idea.
However, I may pick up a new pair of sunglasses. I’ve been using the same pair for 8 years now (a much older prescription), and it seems my left eye is only “marginally legal” with them. Although I have to say, when I read a number plate at 20 metrres, I tend to do it with both eyes.