heatslave 9.24 no pressure following leak?

hi i have just moved into a property that has the above boiler fitted,was all in working order with a small leak on the hall radiator.since then the pressure dial has dropped to zero and have no hw or radiator heat, how do i go about fixing this, is it fixable by myself or do i need to get corgi reg person out?
any help would be greatly appreciated

freezing lady in edinburgh

thanks in advance