Aeris i highly reccommend getting broadband. It'll make your ping really good and it'll help for other things other than FF (downloading files, viewing websites). Standard 56k can usually go about 5kbs. Broadband (512k) can go at about 100kbs. For double the 56k price (around £30-£35 depending on which ISP) you get 20 times quicker.

Don't get Tiscali (It may be really cheap but it is only 110kps)
Get Freeserve (Even though I'm with AOL, freeserve rules, and it's cheaper.) The flatrate is about £25-30