It's quite big in the Scandinavian countries due to its environmental credentials (as long as it doesn't cause a shortage of food intended crops) and the tax breaks it affords the Swedes and Danes compared to the ridiculous price they pay for regular fuels including tax.
Never seen any E85 pumps in the UK. You get a few more horses but it's about 20% thirstier litre for litre so it needs to be at least 20% cheaper for you to be in the same position £-wise to be running it over petrol.
It will only be cheaper if/when available if the Chancellor doesn't tax the hell out of it, petrol is cheap without the tax hit right now, the Yanks sell their high octane petrols for around 50p a litre ($2.80 per US Gallon).