Which jobs are big enough that an architect is needed?

[Saswiss]

Hi hope someone can help. We want to do a little bit of work to the house and want it done properly. All we want to do is partition our garage, extend a small room under our stairs cavity (which currently sits outside the house) to become a study, and move the boiler down a floor. It's a big enough job that I feel that I need a professional to advise whether something is not possible, but not big enough to warrant an architect because their websites always seem to advertise big jobs like basement conversions and building new extensions. Can a builder just do this type of thing without the need for an architect? Or can architects also advise on really small jobs like this? I feel the main thing we'd need them for is advising how we best use the space available to create a study.

We are knocking a wall out in the kitchen, upgrading an alley to a hospitable room and changing a workshop into a utility room. We have a recommended architect to do the drawings with the structural drawings it will be £1500 but we will then have enough to ask a few builders to quote and enough for building control to sign it off.

I am comfortable its money well spent