Planning permission - all at once or in 2 parts

[Singlebutmarried]

We’re looking at putting a garden office in. DH is now permanently wfh, and we want the spare room back.

We’re also looking to extend the downstairs of the house, but in order to do this we need to office in first.

As we want plumbing in the office for a loo/sink/kitchen area I’m pretty sure we’ll need PP.

Bur do we do it all on one application, and can we do the office first and then move on to the actual build a few months later?

I would say put it all on one application form as it will only cost you one fee, one building regs inspection fee etc. You normally get 3 years from approval to get the work completed so I don't see the benefit in separating them out if you will get them both completed within 3 years.

I would do a bit of research into how generous your planning office is. Go on the council planning website, see how many projects gets planning permission first time. Where we lived previously most projects were given planning permission, where we live now they are much stricter.
We put a loft extension & kitchen extension on one plan ( for various reasons permitted development didn’t apply) and did not get planning permission, though the report said they were happy with the design of the kitchen extension. We then split the planning permission and was granted the kitchen extension but not the loft. We are still try to get planning permission for the loft but at least we can start building our kitchen. So putting them together did not work out cheaper for us, as we had to pay again when we split the plans.