Main water inlet pipe stopcock seized. Have tried freeing it to no avail so looking to replace it. It's very old as you can see on the attached pictures. I've bought a 25mm stopcock and have a 1" to 22mm reducer. I can't get the reducer to fit over the black pipe as pictured and I'm beginning to wonder where I go from here, as you can see the black presumably PE pipe has a 22m copper pipe insert.