I suspect I already know the answer. They wrote to me saying it was a year since my last eye test and said I could go for one cheap, so I booked in.
Firstly he asked why I'd come in after only a year (WTF?! They wrote to me and told me to!!) and to not come back for another two years.
The optician asked me early on if I had double vision, and I said that I didn't. He didn't seem to believe me and did some check which involved me taking my glasses off and him holding this light pen thing in various positions in front of me and asking if I could see double. I'm minus 5-ish so couldn't really tell - I just couldn't focus enough to see if there were two, it is all blurry. Also I can only see out of one eye at a time; they don't work together however hard I try and he was annoyed by this.
He said that I have a squint in my right eye which is what's causing "all these problems" (I don't have any problems?), to get new lenses in my new prescription and make sure they're the thin ones and not to do any boxing or martial arts. This I had to question this and it's apparently as my eyeballs are bigger than normal ? I think I'm going to get tested elsewhere.