Rose, We have a King size bed (instead of buying a cot when I got pregnant, we invested in a big bed as we only had a double before that. I never planned on co-sleeping, but I fully expected mornings and occasional nights in our bed). Some people sleep with 2 or 3 kids in a King that has been turned to the side, making it 200cm wide and 180cm long.
It sounds like you are referring to sleeping with an older child, which I could imagie could get quite cramped in a Queen. Doable, definitely, but a little cramped. I don't move much when I sleep, even less so since Maya was born. So DD and I sleep in my half of the bed and DH still has his whole half to himself. So I guess, if both you and your DH make a little space sacrifice, it should be manageable. But older kids often sleep quite restlessly, tossing and turning, so it might not be so easy.
You could try putting a mattress on the floor next to your bed. Or moving their bed right next to yours, if your bedroom has enough space. But that's only feasible if you plan on co-sleeping in the long run. Not for the occasional night.

Sasa