It's a Baxi Bermuda 552 Back Boiler Gas Council reference 44-077-50.
If the burner shuts off after a short period it might be that the circulating pump is not moving the water away from the heat exchanger and an overheat thermostat is triggering - but I know nothing about boilers - call an engineer, preferably an older one.
Good luck...
Peccavi
July 2009
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