Virgin will be offering video on demand soon. So to have caps would make no sense when they plan to compete against sky and freeview for movies (imagine watching a HD movie and and having to wait until the next month to watch the next half). Most ISPs who have caps just don't have the bandwidth, so rather have people who use the internet to read emails than watch videos.
I am also thinking of switching to Virgin or BE who are also planning to relases video on demand.
BT (people who should be blamed and the goverment) are planning there 21st century network which would be out of date when it is finished. Even though i am not psychic it its not hard to see that in the next 20 years the UK is going to look stoneaged when they are compared to Japan, Korea and others.