The Wc

There are a few points that need to be checked if working in old buildings the Wc is often the 1st thing i check which will sometimes help you gauge the task at hand as often there are wc fitted so well they do not need replacement unless broken which is where you can come across pans that have a 180 degree outlet or smaller than 4"  at times fitted to a cast iron stack 

is the pan connected to a cast iron stack ? yes 

then depending on whether the house has a conservation order on it will determine your options older houses generally, this is a indicator that the waste pipe to other services may be copper which involves a different type on connection  to ensure water tightness if no original parts can be sourced 

Is the wc a closed couple type ? yes 

Be mindful as some closed couples are not free standing and will need support for the cistern other than the pan screws 

Is the wc a low level pan ? yes 

with this type of pan you have a bit more freedom as you will have a cistern connected via a 1" 1/2 pipe so you can technically put the cistern almost anywhere