I cannot install external ducting for my cooker hood. Is recirculation a good idea?

Yes. All Whirlpool hoods can be used in ducted or recirculation modes. Recirculation removes unpleasant odours and fat from the air that passes through the hood, and blows the air back into the kitchen. It does not reduce the humidity of the air, so humidity levels in your kitchen might increase. Do not connect a motorless hood to a central ventilation system.