What did you find when you did your own G**gle search for a manual? The only manual I could find fo ryour boiler doesnt show any clock on the boiler:
https://www.worcester-bosch.co.uk/professional/support/literature/worcester-si-ii-operating-instructions
Is your timer ON the boiler? If not, what make and model is your timer?
vbmnxcv, April 2019
