Not much choice 'good' Bluetooth earphones for £40. Most are cheap unbranded or silly name stuff on the jungle site.
MEE make some reasonably decent budget headphones/earphones. I was looking at the M9B, which going by comments do provide good sound for £30, but the downside seems to be poor battery life. I think that's likely par the course with cheap ones.
I am sceptical of how many good user comments the ridiculously cheap ones get on the jungle site. I'm sure most have fake reviews. One pair in particular for £11, have all 5* ratings. Bluetooth earphones for £11 and 100 5* ratings, I don't think so.