I know exactly what your problem is.

You are using Tiscali as your ISP. They are reknown as being anti-p2p sharing. They are also reknown as blocking or shaping p2p (only) bandwidth at certain times of the day.
Hey how about that .... and you didn't even tell me those details. I had to do my own investigation since you didn't do as it suggests above at top of page which is an excerpt from the forum rules. lol
Yes sorry to hear you are using such an ISP. Unfortunately Tiscali now controls many many ISP's underneath it in UK, many/most of whom still maintain their original ISP business name.
Solutions? hmm ... let's think. Not sure changing port works in UK from memory (did in other countries with Tiscali). Changing ISP sometimes works.

But yes you could try changing ports. erm .. not sure which LW version you are using ... I'm sure you will find the option in Advanced options ... Firewall -> Connection & listening ports, change to one between 49152 - 65535. Such as 64049 for example.
Other thoughts? hmm a proxy 'might' work .. not sure if it's ever worked against Tiscali. They still control the lines all the same I 'guess'. But it's still an option. Proxies are rarely fast though. O.o And takes forever finding ones that do actually connect, and eventually you need to find new ones.
A Fix for those whose ISP's block Limewire pages 1 - 3 which have links to alternative instructions.