Hi guys,
I didn't think it was anything to do with settings on a PC because I have multiple machines in the house, all running different setups - some with a fixed IP on the LAN, some dynamic.
It looks like I was correct about this, as after a lot of debating and deliberating, Martin at Aquiss managed to spot something very odd about my connection while the fault was occurring: when pinging my connection, the response was coming back from a different IP address!
I'll mention now that I have a static IP address with Aquiss... and a lot of digging from Martin finally revealed that someone else had entered my IP address in the setup for their router, so they were unwittingly (one assumes) hijacking my address!
Martin has now taken care of this for me and I have the address to myself again. Having done a few tests, I'm happy to report that my connection now seems to be coming back up first time every time (touch wood)!!
Thanks so much to all of you, and especially Martin at Aquiss, who was good enough to stick with me on this one and eventually track down the reason for this happening, which let's face it, was highly improbable and definitely wouldn't be the first thing you'd think of. It reminds me why I'm still with Aquiss: they provide a quality service and have a genuine desire to help their customers.
Tom