I am possibly a little out of my depth here, but as you appear to be U.K. based, it should be easy to try another ISP for free- well the cost of a telephone call. My broadband ceases to function occasionally - probably something to do with my BT line so to check that the problem is not with PPRuNe or some of my other favourite sites, I switch back to that Neathanderthal of internet systems, good old dialup! PPRuNe and all the others then come rolling in but at what speed........ and to think that a few short years ago we all accepted this as normal!
P.P.