If you use Wago 222 and 773 they are classed as maintanance free and are better than chock block. The comments made in previous posts are correct. If in doubt turn everything off. Ideally you need to do what they call dead tests before energising the circuit and because you rerunning “unprotected cables behind plaster board current regs say they should be RCD connected. so you could use an RCBO or move the MCB onto an RCD protected part of the board. You can pay a suitably qualified electrician to test and certificate your work (don’t cover the old switch until inspected). I would also suggest if you do cover and plaster over old switch, measure and write down position and put a note with the certificate.