Hello again Shazzy. I've done a bit of digging around and two things crop up repeatedly.
1. Tiscali may be having problems at their end.
2. Most broadband users have a contention ratio of 50:1. This means that if 49 other people are using broadband on the same line/exchange as you, then your speeds will be slower as the system tries to even out the bandwidth so that everyone online at that moment gets a similar speed.
Like I said earlier, go to the helproom forum and ask them. Some very clever bods in there and some of them are Tiscali users.