Do you think insect repellent injections are worth doing?

We have been quoted £500 for our whole (very small) house. I think they will inject the timber in the floors and maybe elsewhere too.

Does it actually prevent anything?

Unless you can see little piles of sawdust on the floors, you do not have an active infestation. If your house is a new build, it is unlikely you will ever need such a treatment. I suggest you spend your money on something you really need.

Agree with Percy. One company wanted to treat our entire (1900) house for woodworm. The woodworm holes were there but the woodworm were long dead. Unless you have the symptoms percy describes, keep your money.