This is a service paid for by the NHS and operated through local opticians. You can apply directly to a participating optician as well as via your GP. As far as I know, it's available throughout the UK.
I had a MECS appointment on Friday. About a year ago I went to my GP about problems with my left eye. He just glanced and said 'blepharitis' and gave me a prescription for antibiotic eye drops and wipes. It was eased for a while, but I keep having recurring problems. I was going to see the GP again, but read on this forum (Mrs Nails) about MECS and decided to try it. I'm very glad that I did and grateful to Mrs Nails for mentioning the service.
I had a very thorough examination by the optometrist. I was reassured because he was fully aware of GCA and the possibility of sight loss. He told me that at present I have no signs of blepharitis, but explained that it tends to be an intermittent condition and it was worth continuing with preventive measures. However he found that my current problem is caused by a damaged tear film on the surface of the eye, worse in the left eye, but also present in the right one. He said it often happens with aging, but personally I think pred might have helped. He recommended different drops (Hycosan Plus) which seem to be easing it after only three days.
If I'd gone to the GP, I might well have been given a cursory examination like the last time and prescribed the wrong type of drops, or he might have referred me to MECS, knowing the optometrists have specialist training as well as the most up-to-date equipment. Instead I got there straight away by applying direct.
So, if any UK person on the forum has eye problems, I recommend making a MECS appointment. If you search on-line for MECS and your local health authority, you should find the details of the nearby optometrists who take part in the scheme. You can also be sure that if the optometrist suspects something serious, you will be referred to hospital.