I sympathise Ceri. Ours is waterlogged all winter through. If you stand on our path, you can hear the water trickling through it! :o Drains are a no go for us also, same reasons. My Gramps advised using one of those tools which makes little holes a few inches deep, or using a fork, pushing it is, wiggling it then pulling it out to reveal holes, and then brushing in sharp sand to improve drainage. I don't know if it would do the trick and we have a lot of lawn so haven't yet been able to justify it. We just try to keep off it as much as possible. Not a good answer, sorry. Come on lawn experts out there, help! :-/