Thanks a lot for all the earlier info you posted, Charlie, it's was quite encouraging and for now clarifying that for me.
You are right, I have no idea what the eye issue is at all. I'm guessing it's just a defect from poor breeding, perhaps.
I apologise to @AilyNC for being a little bit sharp, but I am standing by my guns with regards to the other thread we have been discussing.
Get the Betta. It's a nice looking fish & you clearly like it. It's not too long a journey from Manchester to London & you can look up youtube videos of posting live fish to send to the seller. Hopefully it settles in quickly & has a nice long fishy life.
I'd love a betta myself but also want too many fish for my tanks