Putting in raised beds.

Hello all,I have recently aquired a plot and at one end are about 18 raspberry canes (good croppers apparently) which wouldn't be too bad but they are choked in couch grass and when I say choked I mean throttled and it looks really messy so I was thinking - I want to put in two 4metre long raised beds but how to prepare the ground?,I was thinking of cutting the canes to ground level and then laying a weed suppressing cover on the ground placing the raised beds on top of this,filling with soil and hey presto but this sounds too easy,would the weed suppressant affect drainage?.I would like to keep some canes at one end or in the middle but get rid of the weeds so can I dig up the raspberries,clear the couch (something I am expierienced in) then put the canes back in the soil?,thanks.

If I've followed this correctly you are planning to bury your weeds and raspberries under weed fabric and build raised beds on top, leaving a few raspberry plants at each end which you will dig up, weed, and replant?

Possible problems are that the buried couch will simply grow back into your newly-weeded remaining raspberries, you will be quite restricted as to what you can grow in your raised beds unless you make them very deep, and drainage could be a problem even using a permeable membrane, partly dependent on your soil type. I also wouldn't want to bet against raspberries forcing their way back up through weed fabric!  

Make sure you find out whether the rasps are summer or autumn fruiting before cutting down the ones you want to keep - if they are summer ones if you do that you won't get any fruit next year, but apart from that now is a good time to move/replant them.

 Thanks for that,I kind of guessed that there would be no short cut but have to dig it out,oh well at least by the time I get to them I should be a couch grass expert.