My silicone, less that £5 shoe covers, came this morning, they fold flat and weigh 111g. They look and feel robust enough for what I think I want them for. I've tried them on and am confident they will be just what I'm looking for and will allow me when hiking to do away with the need to carry flip flops or other heavier types of back up shoes. By trying them on this morning I realise that I will still have to put my socks on whilst in my tent (I can live with this) because the silicone clings to my skin if I don't. Once my socks are on the boot covers slide on easily.
So for me, that will mean I can get out of my tent and stand up, walk on wet grass and then find an easy seat or lean against a post or tree and because my feet will be dry I can then put my boots on without too much fuss. If I manage to get the boot covers insides wet (e.g. in a shower block) I'll just turn them inside out to dry, drying shouldn't take more than a couple of minutes, or I can manually dry them.
All I need now is to go hiking! Not until 2021 I think.