You can use any IPStream ISP e.g. AOL, Tiscali, BT Retail, Plusnet, Orange, Talk Talk, Virgin Media, ADSL24, IDNET, Sky, Zen to name but a few!!!
As for BT Retail whos forum you have posted this thread in I don't think they will mind that usage. Sounds very similar to myself and I have a good experience, with little to no slowdown. Online gaming is good with BTR as they use Central Plus from BT Wholesale which provides them with good if not the best pings around. As for online TV it will be fine with most ISP's well I say most just ones that ask for a decent amount of money each month and don't do a Tisali

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How much are you downloading a month? I must do around 50GBish maybe a bit more each month and have Option 3.
Oh and another thing if you get BT TBB make sure you take the �30 Vision offer its a freeview PVR which can always come in handy. Also means you get to use the Newcastle technical help desk for any issues. They are superb.