have a look on the Worcester web site how to refill
first choice refill the system with water using the filler loop/tap
fill up to 1 to 1.5 bar cold on the gauge turn off filler loop tap.
bleed ALL of the radiators free of air
now check the boiler pressure(will have dropped )
may need to top up again due to any loss through the bleeding of the rads
when system is at 1.5 turn off , and remove the filler loop to comply with bylaws
try boiler
wirecutterman
January 2010