Yes it's true that Tiscali have turned into one of the crappiest ISPs around and what you have suffered is about the same as many of their subscribers on their 8Mbit connection. I have seen on their forums click here that some users have been reimbursed with some money for their trouble but it hasn't been much if I remember correctly. The "MKs" on the Tiscali forums have little power but they can put your case if they feel like it, but you do have to go through the mill before getting any results. Give it a go anyway, you never know. Good Luck.
PS. I would (and did) get my MAC number and move ISP.