So i shall be on a server for 30 minutes or so and suddenly everyone starts lagging? I leave and reconnect and everything is sorted, i've disabled firewalls and anti virus while playing and doesn't make a difference, my internet is ADSL and haven't had a problem with it at all, worked perfectly fine before but not now?

If everyone starts lagging then i think its server issues maybe no ? Is this probloam accures in every server ? Have you installed anything new that may cause this ?

This looks similar to your issue: https://www.lfsforum.net/showthread.php?t=70150

That case was solved by reinstalling Windows.

I got a Packet From Unknown UCID 69 and Packet from unknown UCID 18 error in game if thats any help?