Turn the boiler off, disconnect the condense pipe and put a bowl or bucket under the pipe where it comes out of
the boiler.
Pressurise the boiler to 2bar and leave for a few hours and check if there is any water coming out of the condense
pipe we normally leave it overnight.
If there is water...
Why don’t you get the engineer that service’s it to take a look at it before buying parts you probably won’t need.
If as I suspect you haven’t had it serviced if you post your location there may be an engineer on this site in your area.
For those of us of a certain age, will know what the fault...
We cut them tight to the wall using a 9ins grinder with a metal disc and a vacuum cleaner helps to keep the dust down.
Then fit a cast iron to plastic adapter a short piece of 4ins soil pipe and a straight pan connector...