I think you could learn to replace sockets yourself. I don't know if there is a really good guide to the novice DIYer, though. There are lots of things it wouldn't occur to you to ask because you don't know about them.
Yes, a double socket only has one set of wires going to it. The two switches and sockets have internal connectors to the same terminals. And if the faceplate is damaged, the whole thing becomes unsafe.
Yes, a double socket only has one set of wires going to it. The two switches and sockets have internal connectors to the same terminals. And if the faceplate is damaged, the whole thing becomes unsafe.