Update, and this is cool.
Found a thread by a person who's designed a 3D printable lens adapter.
Link is here:
http://www.thingiverse.com/thing:1602460/#files
These take 40mm diameter standard glasses prescription lenses. So basically, get this printed, amble down to your local optician and job's a good un'
Then found a fairly local service who can print them:
https://www.3dprint-uk.co.uk/3d-printing-service
The quote from this printer came in at £16.40 per unit (in black). Unfortunately they have a minimum spend of £40. So my thoughts were to order 3. One for me, one as a spare and one that I'd probably Ebay.
Ah, the joys of technology.
Any want one?
They've copied what VR Lens was already doing and just made it available to do yourself.
I have prescription lenses for my Vive and they are great