In reply to a post by adrenalize_:

IMHO There would have to be an extremely large amount of interference to stop the network connection negotiating even if dropped down to 10Mbps - I'd work back up the networking route with a laptop or similar to see where the networking gets to.

That'll be my next step

In reply to a post by MrSaffron:

One possibility is that the Ethernet cables are crossover ones, which many devices won't care about but some devices do.

That is possible, but the switch at the other end is a Cisco one that senses crossover cables and adjusts as needed so would be surprised is that's an issue, but I will get out my cable tester.

I wasn't having a very good day yesterday when moving my router from behind the TV and relocating it in the utility room. It started off well as the router is now in a more central location within the house and as a result, there's WiFi signal all around the house, which is great. But for some reason I'd first unplugged the existing cat5e cables from the wall-socket near the TV, then later on plugged them back in after connecting them to the PVR and TV but managed to plug in the first cable upside-down, thus destroying the spring connectors inside the RJ45 module and breaking the retention clip on the cable boot, so the cable is now useless. Cue ordering a replacement RJ45 module and some tricky replacement of the broken module, unless the damaged module is repairable?

I found the cause of the problem after testing the connection between the RJ45 sockets and the patch panel and found that a number of pins weren't transmitting any signal on both sockets. I can understand how that would've happened on one of the sockets as I'd previously tried to plug in a patch cable incorrectly, destroying the connectors in the the process, but the other socket had no such damage done. In fact I'd unplugged the router which used both sockets, one to receive the WAN connection, the other to connect the router to my gigabit switch and all worked fine until I unplugged the cables when moving the router.

Anyway, I replaced the two RJ45 modules (a bit of hassle as it's very fiddly and error prone) and all is now well - both PVR and TV connected via ethernet now and both more responsive with streaming services.

Thanks all for your help and info.