Never heard of them before your post. The destination/recipient countries seem to be a bit limited and they have mixed reviews on UK trust pilot website (23% recorded them as bad...). Think I'll stick with (Transfer)Wise.
I've booked with Dam. There seem to be some good reviews and I think I read they do work for the airport too. Supposed to be test/result emailed the same day.
I've been to my GP who refused to sign/issue certificates, another 2 local GPs who don't want to know and suggested a private clinic (who want £600), 🙄 dispair...