If you want to push the boat out, the custom fit jobbies are Elacin (same bunch as make the ER20s) – also on DaveGr’s link. You can get them for various degrees of attenuation – 9db (ER9), 15db, 25db – tho’ once you have one type you can swap in a different attenuating filter (tho’ those aren’t cheap at something like 70-80 quid, iirc).
Expensive tho’, £170-190 inc fitting, depending on where you go…tho’ I *think* there’s a cheaper route via signing up for the Boots Hearing service (no extra cost) – it appears to bring it down to the 140 quid mark.
A mate and his wife bought a set last year – they go to a lot of noisy gigs too – they had them in time for Download and were pleased with ’em.
I’ve got a pair of the ER20s, but they seemed to have a little too much attenuation – but p’raps I ought to persevere with them a bit more, I suspect one’s brain does a bit of gain correction once they’re in !
I’ve also tried the Alpine Musicsafe jobbies (phil’s link) – they come with a selection of filters – but they tend to cut more out at the top end (actually ,so do the ER20s:
http://www.hear-more.com/musician.htm
The Alpines have a smaller flange than the ER20’s so feel better if you’ve a small lug’ole – I bought the ER20s for my OH but she found them uncomfortable, but it’s probably possible to trim the flange (carefully !)
My OH tends to use some Max foam earplugs – I bought a big bag years ago when I was still riding a motorbike.