Wise move! These days, just moving the light switch as you describe requires you to test the insulation and the Earth Fault Loop Impedance on that complete lighting cct. You will probably find there is no Junction Box. If there were, you would have to bring that up to current regs which mean it has to be readily accessible, ie not under floor boards, in ceiling voids etc. You would have to ensure that all the fittings were as required for the relevant zone and, if your installation is of an age where there earth wire does not exist in the cct, make sure only class 2 fittings were used and, probably, ensure the cct was protected by an RCBO. On top of that, you'd have to attend to any supplementary bonding issues that arose.
And it is correct to say this is notifiable work so, yes, Building Control or a self certifying electrician need to play a part.
P.S. I bet I have spent more time correcting the errors made by self important diy'ers who "knew how to do their own electrics" than your above answerer has corrected made by pro-electricians.