Drain the radiator and fill the rad with inhibitor by removing the top fitting on the rad is how you get inhibitor in there. Ifits a combi, its easy to remove the valve. Just depressurise the system, isolate the other end of the rad and remove the faulty valve. The system will be sealed and work the same way as the plugs I said about above and hold it in suspension. I would speak to your neighbour if he does it as a job. Its a simple job but could make a mess for the un knowledgeable.

Its a simple job but could make a mess for the un knowledgeable.

Hey, hey! What are you trying to say? 😮
🙂

Nothing DD honest :D. But Mrs DD would throw a wobbly if you did make a mess and the neighbour would do it as a return favour.