bathroom - don't know where to start!

[Theknittinggorilla]

I currently have a bathroom next to a separate toilet. I want to use the toilet and some of the (long) hallway to make an ensuite bathroom to an adjacent bedroom. I then want to refit the existing bathroom to add in a toilet and shower, will need to block up the existing door and create a door from a large airing cupboard. And possibly retain the existing shower and bath, but would need to re-enamel in that case.
This will involve moving a couple of doors, adding a small area of wall, and knocking a door through to a bedroom. Its an Edwardian house with thick walls.
Where do I start and who do I need? Do I need an architect? Do I get a builder first? Or a plumber or bathroom fitter?
If anyone has done something similar and can give me some guidance would be hugely appreciated!

An architect is optional, they charge a lot of money but can assist planning layouts, use of space, and creating detailed plans for builders to work from, making the outcome more likely to be as you wanted it, iyswim.

I haven't done that sort of project but had similar confusion over my kitchen. From what I can gather, you could project manage it yourself and therefore employ each of these trades yourself and buy in the fixtures and fittings. Or, you find someone who does bathrooms and has several skills themselves and they subcontract things like plumbing and electrics out, thus they also project manage it. You could also go through a company - a local bathroom shop might be able to arrange a builder. Ive also previously gone through my plumber to arrange a bathroom refit. Then I'd say it depends on your budget. I think my first step would be contacting a local builder who advertises that they do bathrooms and get them over for a chat. Ask them their thoughts and say you're in the early stages of planning it.
After going in a giant circle myself I've instructed an architect. It's costing 1-2k which is tons but I'm removing supporting walls and wanting help planning size of a new bathroom and utility.