I'm going to let GC have a rest overnight here and will try again tomorrow. I will also reset my router to see if that restores warp speed. Thanks, @redstar. Will give that a read.
Downdetector website shows a lot of outages for Plusnet at the moment. We often have a problem at this peak time and have to reboot. It's then usually OK. Hubby is just seeing to his blood pressure tablets then will go on the desktop and have a look. But I think it's Plusnet. I'm going to get the dinner so I'm signing off - but it's OK on mobile so GC must be OK. Happy Birthday FC!