Behaviourist, Karin Landsberg of ThinkingPets sent me this great advice about how to tackle the Battle of the Kingdom of the Couch:
Of course, a compromise can be reached - what about designating one couch with a distinctive cover over it as the 'doggy couch?'. This way, the Beagles can do their thing without all your couches needing covers or constant management.
Easy to teach - if they approach the wrong couch, give a no reward signal, and guide them to the correct couch. Encourage them on to that one, then give a settle cue and let them chill out there. You don't really even need treats as the comfortable lying down will be its own reward.
Thanks Karin for the great advice. Now to implement it!
(P.S. A no-reward signal is not shouting or smacking the perpetrator, but a calm verbal command like uh-uh or if you want to add some South African flavour - sies tog!)