Worcester boiler with dodgy button

Hiya Guys..
I have an old Worcester boiler fitted, and i want to turn the radiator temp button on the boiler to the max 88C not the standard 75C, but it is stuck at the 75C mark, the hot water setting goes to the full 88C but not the radiator one, any ideas, i dont want to break the switch?
Thanks.

 

press the yellow button on the control knob in and it should let you turn it to max

 

It'll use a lot more gas if you turn it up that high. What's your reason for wanting to do it?

 

Thanks for the replies guys...
The house isnt just quite hot enough, we have plenty of rads and double glazing, but thought that little bit extra would make the difference in the very cold spells, her in doors is African and still not got aclimatised to our english weather lol...would it make a massive difference to the gas usage?
Thanks for the input..

 

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