Doesn't Tiscali have a spam filter you can turn on like BT?
I would assume not from you question.
2 practical suggestions
1) change your ISP to one that does
2) it's possible you are getting so many because your name is in your email (eg, johnsmith@etc). A lot of spam is computer generated, and they use name combo's. If you have a facilities for more than one email, devise a name more random, and start using that - that way you'll get less spam, and the "right" mails will be easier to pick out.
Or, just thought, try a spam filter - have a look on download.com, there are some there.