Any plumbers able to help with measuring for a new loo please?

[Paintlayer]

We need to replace this loo and want one with a concealed cistern to hide all the pipe work.

I am looking but there appears to be varying depths and to want to make sure I buy the right one.

where do I measure from to make sure I get the right depth? The wall cladding is being removed so the new unit will go back to the wall.

the waste goes down into the floor ( added issue)

can anyone help please?

It all depends on the position of the soil pipe and you say that's an added issue.
Is the reason for the boxing behind the toilet currently to bring it forward so that it can connect into the soil pipe? If so you may need to move the soil pipe back and the further the better. Ideally all the way back to the back wall. The further you can move it back then the narrower the unit you can have and it must fall within the width of the unit. The way the joists run may dictate how far back it can be moved.

The only important measure is the soil pipe.
Your new toilet's soil pipe needs to be located over it.
How much are you looking to spend because you would need a number of different trades or a bathroom reno company.
If you want to move the soil pipe you need to remove the tile and concrete / wood flooring you will usually need to pay someone other than the plumber to do that.
The plumber will do the plumbing bit and then you would need to have some else to replace the flooring.

You should check under the counter to see where the water feed for the flush comes from. This is not as important as the plumber can install a flexable feed.

If you are looking for a sleek look and taking the wood wall down you could batton and build out the back wall to shrink the room inward to the toilet's tank

The toilet will have to be fitted into the existing soil pipe so I need to make sure it will fit.

ill take the measurement from the soil pipe to the back wall and go to my local bathroom shop. They’ll be able to then hopefully advise the best one to buy.

my fitter is very good at boxing in and making look good so fingers crossed it’ll all be ok