How are you going to chase the wall?
Being plasterboard, if do a long chase you will weaken the plasterboard.
You could try a series of holes and fish the cable behind, if you can hack some straw away. Otherwise you will wreck the plasterboard too much.
I wouldn't cut a slot that long in plasterboard personally, how would you fill it so it doesn't crack?It’s a chase of around 18cm downwards into skirting, can’t see that interfering with the integrity of the plasterboard?
So probably would I (I certainly would not 'chase' plasterboard) - but, for the record, note that the OP said 18 cm, not 18 inches.If it were me, I would use a long thin metal rod to make a hole through the straw most of the 18 inch run.
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