Almost out of curiosity (yes I'm
that bored in Lockdown, and saved
that much money) I bought an antibody test from Lloyds Pharmacy online.
CE-approved, and they reckon very accurate:
External Link/Members Only I got in very quickly because I received a heads-up email from Lloyds, being an existing customer of theirs. Stock vanished within a few hours and I think they've been out of stock ever since.
After the first lancet appeared to give less than impressive results, the application of a second saw me dripping blood copiously all over the kitchen floor

The result came back with 48hrs of me posting the sample.
I should stress that I had no particular reason to think I might already have antibodies, I was simply curious. I also knew that the chance of a false positive was virtually nil. I would also state that had I tested positive for antibodies, this wouldn't have made me feel somehow invincible and go breaking Lockdown and hunting for meat!
By the way, as expected, I was Negative.