is a bathroom designer worth it

[Dumdidums]

i'm thinking of getting a new bathroom and have now spoken to two specialist bathroom designers however essentially what both of them said is to come back with ideas of the sort of tiles, bathtub etc that i want and then they will continue the process.
If i do this and find exactly what i want why do i need a designer ie i could just find a plumber or tiler etc to fit these.
Am i missing something or have i just not found a good designer.
The designers i went to seemed to be fairly expensive ones

We have a husband and wife team fitting our two so I've never felt uncomfortable being in the house with them on my own. But it has already taken longer than the month scheduled. Good advice from previous poster about going away for a week/few days while there is no loo available.