The flexi pipe on my mums hot water tap is gone in the bathroom and I need to replace it but I'm having difficulty turning off the hot water. I have isolated the main feed under the kitchen sink. Went up to the attic and there is a stop cock which is not budging at all and 2 other red valves. I have attached a picture. My question is if I can't move the main stop cock shown can I use either of the 2 red valves to isolate the mains hot water? Sorry I'm not very savvy!