Bathroom light switch/cable in stud wall

Is it modern practice to instead of fitting a ceiling pull cord switch, to fit the light switch on the outside bathroom wall? this will be on an ensuite.

Also when running the cable to the light switch, inside the stud wall, am i correct in reading the regs, that because it won't be 50mm deep, it's ok to purely RCD protect it, or will it need RCD protection as well as an earthed conduit?

Thanks

It is entirely your decision on where you put the switch, if you want it on the outside then fine. if you have kids then it might be better off inside, in which case it is recommended to use a pullcord although in certain positions a switch is allowed.
Concealled cables burried less than 50mm directly in the wall in safe zones in will require RCD protection to comply with the 17th edition regs. These do not need to be in earthed conduit.
This work will be notifiable to your LABC (England/Wales) under part p of the building regs.

Thanks spark123, the LABC are already notified, so no worries on that part.
In that case I think i'll go for the outside switch, its a bit neater IMO. And thanks for confirming my thoughts on the RCD details.