The Umarex Desert Eagle mentioned above would seem to suit my wants Thanks for the suggestion. It's fairly long and according to youtube, weighty. Long means good distance between rear-sight and fore-sight, weight should help with steadyness when shooting. They are not cheap. But why cumbersome?
A bit of faff is not a bad thing considering these guns use a lot of CO2. Faff would extend the shooting session time. Not wham bam thank you Mam.
For cheap there's the Gamo PT85. A small CO2 blowback rifled pellet pistol with white dot sights. One dealer I spoke to said they don't sell them because of faulty returns. That's why I've not bought one (yet?). I wonder whether that's the real reason. It could well be. You get what you pay for. But I'm not looking for perfection, just a bit of accuracy and fun.