Re the kitchen install, from the description given, I wouldn't be giving the original sparky consent to cross my house threshold again, let alone be given the opportunity to do the job properly as he should of done in the first place.
I would be advising the customer to have an EICR done on the electrical work. Then, dependant on the contract with the Bird people, seeking redress from them. If the client employed the tradespersons directly, then dependant on the report, consider taking the matter to a small claims court. After all, now the kitchen has been installed, its going to take more time & money to rectify.
Re the appliances, the Consumer Rights Act entitles a customer to a repair,replacement or a refund. Looks like the client has chosen repair.