My statement is correct according to the UK Government. Holidays and leisure are not permitted. If you had actually read my statement it also says "Legally permitted reason to do so". So I fail to see your problem. By the way the OP does not mention the reason his friend is coming to Thailand.
See the UK.Gov website which clearly states "Under current UK COVID-19 restrictions, you must stay at home. You must not travel, including abroad, unless you have a legally permitted reason to do so. It is illegal to travel abroad for holidays and other leisure purposes".
Yep, I have been unable to do it since I changed to a new passport, three years ago. Basically they said I needed to leave the country and return on the new passport.
As far as point #3 goes, your branch should be able to do better than that. I get my letter within 45 minutes, a friend with BKK Bank gets his within an hour. Not sure about CW but Samut Prakan requires the letter to be within 24 hours of application.