Who do I need- builder, architect or someone else?

[ojbsmum]

We have just moved to a house with a downstairs bathroomand would love to see if we can squeeze a shower room in upstairs. We have an idea of how it might work- building a bit extra landing to fit it on the landing but not sure how this would affect light and the feel of the upstairs, so would like to get ideas from professionals too.
So should I call a builder or an architect or is there another trade I don't know about?

[123rd]

Firstly I would speak to a builder- do you know any that could pop round? Just ask if its doable, and a ball park estimate.
They may suggest getting architect etc involved

[MrsTaraPlumbing]

Someone who specialises in bathrooms.
Probably a plumber but specifically a bathroom specialist, not general builder or general plumber...
If you are in Kent (up to SE london) you could consider my company!

Otherwise look on places like Which?trusted trader. I'd look under plumber and ask for local recommendations.