Well, thanks to this thread I ended up here: https://www.audiobudget.com/ and am now the proud owner of a pair of Rock Zircon earphones (£12.99 from Amazon).

They have absolutely no right to be that good for that little money - I have a paire of Shure SE115s that I bought (a few years ago) for half price (£50) and the £13 Rocks are (in some ways) nicer to listen to. A bit warmer, more bass and smooth where the Shures are very detailed but possibly a bit tiring.

The noise isolation is top notch too - I can hear virtually no external sounds.

I'm now seriously considering acquiring some of the other models on the Audiobudget leaderboard - considering most of them are less than £15 a pop - what is there to lose?

Cheers,

Mark C