Instructions:MyMovieStream are re-branding as OUTNOW, and they have a 3 months for the price of 1 offer at the moment. The upfront cost is £12.99 for three months membership, on the 2-disc DVD package. Cancel after 3 months, or pay £12.99 per month after that.
UPDATE (1 Sep): I have been with this company for two and a half weeks now. I do not advise signing up to them. They are slower than lovefilm to send / process discs, but even worse, their list of available titles is very poor. Note only that, many of them once added to your list show up as "there may be a delay" or "there will be a long delay". This is not just for new movies, but even for older ones - eg. Family Guy, 24 series 1, Phoenix Nights, etc. Even at 3 months for 1, I don't think they are worth going with.