I don’t kid myself that this will be of any interest to most of you, but I finally chose my tent.
After much research and some deliberations, I decided that the Vango Beta 350 is the best combination of my criteria. It’s a 3 person (technically, although the usual advice is to get a 3 person tent for 2 unless you’re backpacking) and has loads of porch space. It’s a bit heavier than I wanted, but I’m unlikely to be carrying it too far and if I am, it’ll be just over 3 kilos each which should be manageable, I would think.
I found it only for £55 (RRP is about £95) for last year’s model but they had sold out. Eventually found it for £60 which isn’t too bad. Vango are a good make so it should last a few years.