My 6yo has started getting severe rash/hives/blisters on contact with items including new clothes & plastic pool noodles. mild,less angry rashes inbetween. we are referred to a derm but its a long wait (uk). anything we should avoid meanwhile?

This sounds like contact dermatitis and you need to try to avoid whatever makes the rash occur, as difficult as this likely is. Find a mild detergent that hopefully doesn’t result in the rash and don’t change detergents. You could try a hydrocortisone cream that you can get over the counter for the more severe rash areas. Good luck to both of you!