If that lot it is being plastered over then they will almost certainly be covered with a plastic capping in due course. I can only think this is a temporary arrangement until the electrician has bought some more capping / found the time to fit it/ finished running cables in the vicinity. However, it isn't compulsory that cables are capped (at least, not to my knowledge). The plastic capping is only really there to prevent damage whilst the plastering is being done.
You're the customer.
No one can claim that that is "good" workmanship. Just tell 'em "come on guys, get some proper clips or capping and do it right please". You don't want to be Cucumbering about with flaking plaster for the next decade.
And take photos of anything you're unhappy with so you can query it with whatever Part P organisation they are registered with.