Worcester Bosch Greenstar 42CDi EA flashing?

Could be the pressure but flashing EA indicates a frozen condensate pipe.
If the pipe freezes the condensate drain water backs up into the boiler combustion chamber. Thats why it locks out and flags up EA.
As its not freezing it could be that the pipe is blocked.
As a last resort the condensate pipe conection under the boiler could be undone to see if it is holding water. If he pipe is blocked the boiler could be holding up to a pint of water.
Once it is all cleared the boiler will probably go into 'low flame' mode for about 10-15 minutes before returning to 'full flame' mode

GB in Wales
February 2013