I find that the Tiscali Speedtest often gives an optimistic result from the first run but settles to a more consistent figure after that. As oldbeefer2 says, the contention ratio plays a big part in your download speed, just see the speed drop when the kiddies get home from school and start downloading their mp3 files. Your distance from telephone exchange and the quality of the connection between your home and the exchange also play a big part. I had an "Up to 2M" Tiscali account and rarely got above 1M. I upgraded to "Up to 8M" at the same cost and now on a good day get just above 5M.
i am with pipex homecall which uses ticali for its service and to be honest i get 5.3 meg up till 16:30 and then it dies to around midnight when it picks up again so yes it will be great during the day it will be slower at night mine has dropped to 90k on occasions. do they throttle it will i think they do