Non ED visa is an option, although personally I couldn't be arsed with it. I haven't been in Thailand for a couple of years but I know the best option used to be Non ED for learning Thai, but I've been told the going rate was about 35-40k baht for this visa a year ago. Don't know if the prices have changed recently. Regarding the METV, this is definitely not an option at the moment. Crossing borders with quarantine restrictions isn't feasible. The best option would be the Special Tourist Visa if it gets continued, unless you want to stay for longer than 270 days. Just make sure you're double jabbed and have £5k/$7-8k in the bank for the application.