There are a lot of companies that install home offices and a lot of them will wire the new office for some sockets and lights as they build it. It's not ideal as you should be using a registered electrician for this sort of work but from what I've seen, the first fix by these companies is usually compliant, although often not the neatest!

We recently installed a new supply to a garden office that was wired by one of these companies. Initially we left some ducting on site for our clients landscapers to lay as they do their work, it was recommended by Josh that they have 2 ducts installed, 1 for the power and another to future proof the installation so if they decide the wanted internet at a later date, it would be possible to pull a new cable in without having to dig up the garden. 

The office installers didn't wire it how most electricians probably would have but that's fine, we adapted and still made a tidy job of it. The picture shows 2 fused spurs, one for the sockets as this was spurred off a ring final circuit and the 2nd fused spur is to fuse down the lights. 

The armoured cable was glanded off neatly and there's plenty of room to work in the weatherproof box. Job well done!