Looks like a strange one this

Could be DNS, maybe an MTU/fragmentation issue, but this should be rare especially if the modem/router have been taken out of box with no adjustments made.

If I were you I'd try browsing the web for an hour or so with the wireless switched off, by ethernet cable (a different one to the one that got the WD40 treatment), in a different socket on the router.

See if that is any better.

If not, then do the opposite, use wireless only for an hour or so.

Also do speedtests on both ways.

If that still doesn't fix it, then at least you have ruled out your ethernet cable and wireless. It could be the PC (not likely if it was working before you had fibre installed presmung you made no changes - with exception of fragmentation issue), or, it is the modem and router as you initially suspected. As long as you haven't made any changes to the modem or router, then you could ask plusnet to see if they would swap them out. Ideally, if you have a spare computer in the house, it would be best to try that first.

Basically if you can ensure that the experience is the same regardless of PC/ethernet/wireless in your house - you can point the finger at the router and/or modem, and at that stage plusnet shouldn't mind sending replacement and/or doing some tests.

Well when it was first installed first thing this morning as I say it took 4 hours to come on, even then I had to ring Plusnet to get them to manually activate it as they said for some reason the automatic activation failed.

Afther that came the ethernet issue on my windows 7 desktop and windows 8 laptop.

I would just use wireless but I get terrible speeds with that, about 15 meg desktop 44 meg laptop yet 60-75 meg ethernet when it is working.

OK, safe to say wireless needs to not be used for any further tests.

Were Windows 7 and 8 computers connected to the router via a different cable and different port? Important to not confuse issues (my fault that one)

Might be worth phoning them up tomorrow and ask if they can check the router remotely (believe they can) in case the config is goosed. Sounds like they had not enabled your username and password in RADIUS or something.

Edited by Pipexer (Fri 13-Jun-14 00:06:33)

Hmmm as soon as I connected the cable to my gigabit switch instead of direct to pc all the issues have gone.