@mary443 - I think if you want to use an architect and it fits with your scope of works, then you definitely should!
Agreed that a CAT can do the work for you though, whilst saving you a lot of fees!
If you have neighbours who have completed similar work to what you hope to achieve, you can use these designs on the council planning website. So, if you see/want a simple loft dormer conversion and rear ground extension, then go with this route.
However, the right architect will bring vision and experience that could be valuable to your project and space. It will cost more but potentially worth it if you plan to live in that space for many years to come.
If you do opt for an Architect, my only word of warning would be don’t be suckered in by a flashy website and big, fancy firms! You should be able to have an initial FREE consultation with any architect, who having seen your brief, can give you a full ‘quote’ with breakdown of staged payments for their services.
I think choosing an freelance Architect has a lot going for it; they can be more competitively priced, you guaranteed 1-on-1 contact time (rather than your project potentially being palmed off on an associate or junior at the larger firms) and unless you need specialist experience, like renovating a listed building, they should have more than ample experience. You need to do your research by tracking down references.
Good luck!