ask around for an experienced local electrician by personal recommendation, and verify that they are a member of a Competent Person Scheme (ask which one, and look them up).
A good way to fit kitchen sockets is to have a row of them, about 150mm above the worktop, with the cable running horizontally between them in conduit under the plaster. This makes them quick and easy to fit, and you can have the switches or FCUs for your undercounter appliances and above-counter extractors and lighting, in the same row. If you decide to add an extra one later it is easy, because you can cut into the wall and use the existing conduit in the same row. IMO a kitchen should have a row of sockets and switches going all round the room, at intervals of 600mm or less.
Only the first and the last sockets on the wall need to have a cable going down to the floor (or up to the ceiling, wherever your circuit runs).
This is easier and cleaner before you have the wall tiled. If not, it will probably need (at least partial) retiling afterwards.
If you don't want to hack into the walls, you can have surface mounted sockets, but these are less elegant.