The box arrived. There were no screws. Three tubes of grab adhesive. They could be a substitute for screws in some situations, but they're not what I was hoping to use in this situation.
Fairplay to Screwfix. People make mistakes and they immediately took theirs on and will be sending replacements for tomorrow. Sadly, I can't do the work now until Friday. However, I can at least cut the boards to fit beforehand.
Oh, and Southern Electricity rang and asked if I wanted to switch back again. I told them that I wouldn't, regardless of price, since on the two previous times they've rung me about switching, I've had their operator either shout down the phone at me, or be very rude. The guy was apologetic. I told him it wasn't his fault and he was, in fact, very polite. It didn't make me feel any better.
Still in a mood today, then. Frustration.
Even my desk phone doesn't work.