Hello dwarf and welcome to the forum I don't know about the slime on your lettuces except that they might be rotting down a bit, separate the leaves and wash well, you may be able to salvage something edible. Garden produce is never as pristine as shop stuff, but then we tend not to use the chemicals that their farmers use to have a commercially viable crop.
The peppers in Yorkshire where you are, I would put into 8 inch pots and keep them in the green house, or a sheltered sunny part of the garden, make sure they do not dry out. I start feeding mine tomato food when they are flowering. Other gardeners may do it differently.
Good luck with it and keep us posted