Hiya Meggles
Lovefilm do downloads of films at a price I think £2.99 each - the settings they use ensure high quality playback on most devices and screen resolutions etc.
There's probably other 'official' outlets similar to this where you can pay for and download movies. places like Amazon, walmart and 'big names' places - do a yahoo or google search to see who and what is actually Live, available, and most importantly available in the UK!!!
Movie downloads is still a hot topic due to possible piracy etc etc so thats the reason legal downloads are scant.
If you want to download (illegaly) from bit torrent sites etc, then other's who know how to do that on the entertainment board may be able to help you out. I do beleive however there are sites which offer legal downloads using bit torrent.
Lastly, if you are after recent blockbuster or mainstream hollywood movies etc then the paid for route is the best way, but be aware there's not much choice as to what's available. Personally, I make backups of all the Commercial DVD's I have, so that I can stream them over my home network, i can convert them to fit on devices like PSP or Ipod or Creative Zen video players - and it means all my orginal DVD's are safely stored away in the loft. Technically, what I do is illegal, but for personal use there's not much risk if i get caught - it's only if I try redistributing those moive files for financial gain is it considered serious crime.
there is software available for around £30-50 which will do as i describe above
So to sum up, your choices are limited - many people will say just download off bit torrent, which is fair enough, be aware though, even if you are downloading 'Pirates of the Caribbean 3' and it takes a stupid amount of time to do so, at the end of it, dont be surprised when it turns out to be Jaws 1 or something ! (you never know what you'll actually get until its fully downloaded and you check it !)
Good luck !
DtM! West London & Slough UK!