After looking at the Ray-Ban deals on the US Amazon site, I decided to have a look at the UK site and spotted these - direct from Amazon and it's the cheapest they've been.
In order to get them for £48, you must sign up for the Amazon fashion newsletter and use the 20% off code (link comment #1). You can create a new account if you have already used it in the past.
It's not clear but I think the model no. is 2140 - Original Wayfarer and they probably aren't polarised.
Size medium only. No measurements given but it's free returns.