These types of regulations are for new buildings solely and don’t apply to any un-inhabited areas for example the Kitchen.
The actual heights which electrical sockets are fitted in new properties has become covered by regularions, so if you’re developing a new home you definitely are required to follow the new regulations. Building work or home improvement also building an extension doesn’t imply that you must install your light switches and electrical sockets to the new heights, you can just install the new sockets/switches to correspond with the current sockets/switches.
Generally an adequate height between the bottom level of the socket outlet and a worktop will be 100mm.
prior to working on any electrical circuit you will need to make sure that it’s isolated appropriately and should not unintentionally end up being switched back on.
If you aren’t 100% certain what you’re doing contact a qualified electrician. Building regulations are changing on a regular basis and altering your house electrics might be against new regulations and may even invalidate your property insurance policy, if uncertain check first!