As requested, here is a picture of my porta-booth.
I have been using it for most of my recordings recently, which I do in the larder. It’s not a great room for recording, as it has far too many hard, reflective surfaces in it, but the porta-booth does a good job of damping down the echoes and liveliness of the room.
Why do I use the larder? It’s the only room in the house where the (loud) sounds of the passing traffic don’t penetrate (very much). I still have to contend with the fridge and the boiler, but Noise Removal in Audacity does a fair job of dealing with those. And it’ll only be the fridge in summer.
A compromise, but one I can live with for the moment.