The following, from another forum may explain your speed issues:
Regarding the current issue affecting parts of Scotland and Northern Ireland, We have spoken to BT who have confirmed that there are transmission (cabling) faults between Edinburgh-Birmingham and Carlisle-Glasgow affecting parts of Scotland and Northern Ireland. This has resulted in BT to reroute traffic over the networks, In turn this is causing the speed issues that some of our users in theses areas are experiencing.
And
From what I can work out there are 2 issues going on.
BT issue, which started yesterday and quite well documented here in this thread, and a routing issue (maybe Telia), which seems to have started a short time back, but has got merged into this thread as everyone is trying to establish a pattern.
Notwithstanding the forgoing, Tiscali does not have a reputation for scintillating performance.