Thanks jetcollie. Good article, I need to read it again for it to sink it. I'm using a D Link DSL 300T that replaced same model D Link I already had, just out of guarantee when all this hassle started, replaced foc by my ISP to see if it helped to stabilise my connection. I don't know anyone with a laptop who could help out as suggested. PC is perfectly behaved once I have a connection, the only gripe is the intermittent loss of Internet access. Speed isn't a problem as I don't play games or download large files, reliability is more important.
Not really knowing the difference between a broadband modem and a broadband router it's a question of just trying everything till I get it right. Bit difficult when a PC thickie.