Gas and electrics
Gas: connecting a gas hob or cooker, or any gas pipework, must be done by a Gas Safe registered engineer.
Electrics: fitting a built-in cooker isn't notifiable on its own, but if it needs a new cooker circuit, that circuit must be done by a registered electrician or signed off by building control. The same goes for any other new circuit.
We have access to registered engineers who can help, and I'll say so before I quote. No surprises halfway through.