All that, and no mention of wazzock, probably my favourite mild insult and relatively unheard it would appear (it was was quite popular in parts of the UK's north in the 80s & early 90s but I don't think it travelled internationally and has since largely fallen back out of use even here). It works particularly well with the common extension "great steaming" as a phrase of exasperation: "you great steaming wazzock" (for full effect: say slowly, in one sighing breath, emphasising each word more than the previous, and take a deep disappointed breath after).

> for full effect: say slowly, in one sighing breath, emphasising each word more than the previous, and take a deep disappointed breath after

I tried that and saying the last word made me exhale enough to force me to immediately take a disappointed-sounding breath, so I guess it works as designed?

If you don't feel the final breath feels intentional enough, too much like you are just out of breath, add a head nod. Though I find that sort of exasperation gets the message across better if looking directly at the subject of it.