oooh, plonker! Nice ring to that, Imma use that one.
wait, is it NSFW? I still remember when a British co-worker set me up to tell a project manager to stop wanking. She told me it was similar to whining. I am still looking for her.
John (affectionately) called Maria a numpty on IG a while back - that's another super descriptive, you Brits have the market cornered for the most satisfying derisive name-calling. She called him an old fart in return, but that's everyday Americanism. We are chock full of old farts.