Boiler overheating - Worcester 280 RSF?

Problem started a couple of months ago. When hot water was run the pilot did not always light. Had to turn tap on and off a few times.

In last couple of days, boiler is constantly overheating and cutting out even when heating on. Need to keep pressing trip button.

Checked pressure valve, showing 1. Have tried opening pressure taps on a flexible pipe, nothing happening. Usually you can hear water running through.

Can anyone help? I am a woman who does not know much about central heating systems but would like to know if this problem is likely to be costly.

Thanks