After battling couch in my garden beds for what seems like forever I've
decided to change my approach to the garden. I want to put in (or have
someone else put in) some raised beds. However I have some questions:
What wood is best to use? Railway sleepers? How high should the beds be to
be effective?
Would you first try to kill the couch where you are going to put the beds or
just put it all straight on top?
What sort of fill/soil mix would you then use?

Thanks

Liz