(Please folks, correct me if I'm wide of the mark here).
If you are set on flying in the UK with a PPL rather than an NPPL, but you fail becasue of your eyesight, you could possibly opt for laser corrective surgery. (I can hear people sighing as they read this, sorry). You would need to take advice on which types of laser corrective surgery are best for flying (contact the CAA medical department on this, and your opthalmic practictioner). I was originally worried about this matter myself, but I turned out to be within the limits thankfully.
The other option would be to set you sights only very slightly lower (is that a pun?) and just realise that NPPL is just as good as PPL as far in that you'll can enjoy the freedom of the beautiful blue skies of the British Isles the same as a PPL, but with the added bonus that your licence will not expire, and you will not need to pay high fees to see an AME every few years. These are some significant advantages then in the NPPL over the PPL in financial terms over a lifetime, and who knows, it may mean that you can carry on doing it for many years more than someone that does the PPL.
Would you really choose to fly though rain and cloud? I rather drive my car in clear weather rather than fog...
You may find that after completing the NPPL that you get a real love for PFA aircraft, microlights or some other aspect. As my dad says, "don't close a door until it's closed for you", and then as my wife says "have you washed up dear?". So, you might just get out of the washing up whatever flying you do (not worked for me yet, but still hoping).
I'm doing the PPL only becasue I can, but you'll read plenty of gripes on here about the red tape of the CAA, so you may just enjoy the freedom of NPPL. I may just 'upgrade' to the NPPL one day...
Tiggermoth