Convert Garage to home office

[BestSchool]

Advice please.

We have a prefab type garage with asbestos side panels, flat roof.

I would like to have it taken down and a brick built home office instead.

I have no idea where to start. Do I need to find an architect? A builder? Some kind of planning permission?

TIA

An alternative, could you have a purpose built home office in the garden instead?

You might need planning permission depending on the size and location of the building, and whether you are located in a protected area - conservation area, aonb etc.
This gives you a rough guide:
https://www.planningportal.co.uk/permission/common-projects/extensions/planning-permission if attached to the house

https://www.planningportal.co.uk/permission/common-projects/outbuildings/planning-permission if a detached building

You will probably need approval under the Building Regs.