I'd sooner go out in that storm in ill fitting metallic Jimmy Choos with a roof aerial strapped to my head than use iii for anything, but that's a personal, highly prejudiced opinion largely based on the appalling speed and functionality of their website. Prejudices aside, I still believe there are better brokers.
Halifax, Comdirect, Selftrade, TD Waterhouse spring to mind.
If u plan on dealing exclusively and frequently online Interactive Brokers would have my vote, despite the tedious application process, as they have very low commissions and a good platform, though I think u pay £10 a month for UK Level 1 real time.