Replacement toilet quote

[Jilly]

Hi a pensioner I am friendly with has been given a quite high quote for a new loo in a downstairs cloakroom, and I wonder if there is another way round this. 
After removing the old toilet, he gave a supplementary quote of £1.8k to change the flooring and fit the new one, so she had to tell him to wait.

 

Here is a photo of how it’s been left. 

He’s suggested removing the wooden floor because the concrete bit where the loo sat is uneven. Fair enough, but the wooden floor is in reasonable condition, so could the old loo space be filled and made good to take the new one? 
 

Any other reasonably priced suggestions? A concealed cistern might have covered the exposed floor at the back, but the new loo has been bought now so some solution to cover the gap at the back will have to be found.

 

I hope that makes sense😊