How high to set the boiler?

I had a brand new Worcester boiler fitted in the summer and the installer left the water temperature at about mid-way on the dial. He said that it would need to be set higher in the winter. Is the setting in the photo - my latest effort - about right or should it be at maximum at this time of year? I'm a bit reluctant to go for maximum as I expect that the water will be near to boiling but I don't really know what to do.

Set it to whatever level you want it set to. What's comfortable for you when you run the hot tap and hold your hand under.

FYI mine is set to 56 degrees

It should be set to the lowest level which still keeps your house at a comfortable temperature. Higher is less efficient and therefore more expensive to run

Where it is will be fine . Dont want it too low as it will take ages to hit target temps .You have a cylinder stat and a room stat ( I assume ) that will take care of the rest

If you set it too low your hot water will suffer, it should be set at around 70c flow (a bit higher than you have now)

Your hot water temperature is controlled by the thermostat on your cylinder. The house temperature will be controlled by a combination of the setting on your room thermostat and trv settings. The boiler thermostat, as in your pic, controls the temperature of the water going through the radiators. If its set higher, the house should heat up quicker from cold. If your radiators are sized on the smaller side of specification, you may need to have them running a bit hotter on the coldest days to get the house up to temp. Generally speaking, the lower you have the boiler stat set, the more efficient the system will be. I would try setting the boiler stat at about 2/3rds and then adjusting a bit either way depending on how the system responds and the house feels.