Central Heating Issue

[holiday1nn]

Hi all, I’ve got an old school open vented boiler with cylinder in first floor and 2 tanks in the loft type system.
Shortly after the boiler fires it gets noisy and there’s a lot banging from the pipes directly above the boiler and around the pump, after 30 seconds to a minute boiler goes into standby (light turns flashing red).
Last couple of times this has happened, the boiler has been off for a day or 2 but then restarting it the system seems to work ok. It's been a couple of weeks and started playing up again yesterday.
Plumber thinks its sludge/debris in the pipes – recommends me to move to a combi system; other plumber recommended replace boiler and pump.
No-one really mentioned a flush or clean but not received full quotes yet.
The system is currently running ok, is there a quick fix? could I try an inhibitor? Or is it too late for that?

Sounds like insufficient circulation, either pump is struggling, pipes and/or heat exchanger are furred up in places and causing some kind of air lock. Then the water won't flow through the boiler properly so it boils and bangs.
I would say the solution of replacing parts is more likely to work but you could always try power flushing everything, and testing and replacing the pump if necessary as a first try you'd need the power flush anyway for a new pump or boiler if there are any blockage in the pulling