System boiler hot water and heating only getting Luke warm

[DTG plumbing]

Got a job to go and check out, it's a system boiler and its only getting the radiators luke warm.
thermostats are up, thinking it could be the boiler stat or perhaps heat exchanger is blocked :/
any help please guys and ladies

 

[Mike Jackson]

Could be all sorts of things, stats, thermistors, customer turned it down, not enough gas, boiler too small. I'm afraid my crystal ball is playing up at the moment so I can't be any more help.

 

[hammers4spanner]

Could be anything that , any idea how old boiler is??

 

[DTG plumbing]

Around 9 years old. I serviced it last week, gas pressures all ok, boiler is correct size. Think the boiler stat and the thermistor off that is first thing to go at. After checking the obvious e.g room stat etc