Replace cylinder or boiler?

[johnnyfastone]

I currently have an old(30+ years) central heating using a back boiler.
Been getting knocking when radiators on and have been advised by professional that hot water tank is an Elston tank which is very old and not working properly, this tank is corroding the system and causing the build up of sludge in the system which is leading to the radiators not heating up and the banging sound. The engineer could not say how long the system will last before it stops completely but he says the only solution is to replace the hot water tank to a mains pressure hot water cylinder which can then be flushed through. Total cost for work around £2000
My question is would I not be better to get new combi boiler rather than replace the the storage tank?

 

[dcawkwell]

Tell this cowboy to get lost.
You can have a whole system in for that.

I suggest opening a drain valve on the central heating and allowing it to flush for a while. A litre of chemical cleaning in your header tank and perform same again should clear out the system.
At worst a new copper hot water tank costs about £200-300.