Clare Newsome:
He's not wrong. Cheapest i'd go is the Sennheiser PXC150 pair, which you can pick up for around £55 (they're OK for the money, but don't fold like their superior siblings).
But for that money you could get a seriously good pair of in-ears from, say, Shure - the Award-winning SE110 in-ears are excellent noise-isolators you can buy for bang on your £50 budget....
hmmmm....seems like i might need to up the budget, anything spring to mind if i can double the budget to 100 notes?