... well, I have taken a punt. Here is my buying experience if anyone is interested.
I went for two pairs in the £69.00 range, so the total for the order was £35.00 - I went for completely basic lenses (there were various add-ons if desired). I then simply copied the details from my prescription. There was one field which wasn't included ('BVD') but there was a free format field so I added this info there. A quick google says this field applies to stronger prescriptions - it's for my left eye which is -5, but it's not listed on prescription for my slightly better right eye, so guessing -5 is the threshold.
Also, my prescription gives my left axis as '3 1/2' - I couldn't enter '3.5' as the field only accepted whole numbers, so again I included this info in the free format box.
The site took contact details and says they will contact if needed.
As stated above, I chose frames in colours I wouldn't normally choose, but went for styles I have had before, as I know what suits my face (not much, sadly). There is a 'virtual try on' facility, but I've tried similar before with other opticians, and not found it gives a true picture compared to trying the glasses on, so I stuck to frame shapes I'm familiar with.
For £35 I'm not too bothered if this turns out to be a failed experiment but I'm hoping I might just have added a bit more variety to my life
. I would readily spend £35 on, say, a skirt that I might only wear once a fortnight and I have to wear glasses all the time, so extra pairs, if they're any good, will be a great bonus.
ETA of glasses is 7 - 14 days so I will report back when they arrive or if I have any contact from them in the meantime.