Decorator not turned up for the third time...

[Wisteriac43]

The first two times were decent enough excuses, but now is just a total no-show. How do I politely say 'please don't bother turning up'?

Just simply say that you have found someone else to do the job since you need someone you can rely on.
After no show for 3 times you don’t have to beat around the bush, they brought it upon themselves and they know it. Most people probably would have canceled after 2 no shows.

Exactly as pp says. It's a bloody nightmare trying to get reliable tradespeople at the moment, it seems. Were they a proper company or a "jack of all trades" off FB, out of interest?

Just simply say that you have found someone else to do the job since you need someone you can rely on.
Don't do that until you actually have found someone else! You could be cutting off your nose to spite your face.