I use a DYE I4 mask. Technically a paintball mask, but amazing. No fog whatsoever, plenty of room for any of my glasses, the fan actually works to keep fog off glasses, many customization options, etcetera. Pricy though; my kit cost about $300 for the mask, fan, extra lense, and visor.
Unfortunately Amazon UK doesn't have the all-in-one option, but those should give you plenty of options:
http://www.amazon.co.uk/s/ref=nb_sb_ss_c_0_7?url=search-alias%3Daps&field-keywords=dye+i4+mask&sprefix=dye+i4+%2Caps%2C238&rh=i%3Aaps%2Ck%3Adye+i4+mask