My internet is an "up to 8mb" ADSLMax connection, but I average around the 4.5-6.5mb range coz of my distance from the phone exchange. And my ISP (Plusnet) recently told me that i'm going to be upgraded to "up to 24mb" in May 2009 for free. I can't wait for that, although I think they're going to change the hours when I can get unlimited bandwidth, which will sour things a bit; I currently get free bandwidth between Midnight and 4pm, but my download speeds are temporarily slowed until the next billing month if I get close to my peak time bandwidth limits. (20Gb per month)
My package is Broadband Premier (Plusnet don't offer it to new customers anymore, but they've got newer packages with longer peak hours but more peak-time bandwidth) and it costs me £21.99 a month with a 1 month contract. The service i've had has been absolutely fantastic and i'd definitely recommend Plusnet to anyone in the UK.
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) so i guess that is why. I only have 1mb down, for most people this is fast enough. But it is better then isdn and stuff like that, and really, really cheap.