Thank you all for your input. I have realised I was barking up wrong tree. American or Canadian- designed dishwashers definitely would cause problems.
I googled "Countertop dishwashers in UK" (duh, as they say!) and have come up with one that is way above all the others in recommendations. (it's a 'Klarstein Amazonia A+ Mini Dishwasher, 6 Modes (Mini, Black, Buttons, 6 Modes, 49Db, A) [Energy Class A+]') for anyone who is interested. They say no real installation problems. We'll have to see. But I really am keen to pursue this. Apart from washing machine , it seems to me that it's the one appliance we'd be crazy not to move heaven and earth to get! had family here yesterday. Both husband and I spent hours in kitchen afterwards. Thanks anyway. I'll post progress if anyone interested...