My house is a Victorian brick built semi, with 3-window bay on ground floor and stone sills. The corner of the sill nearest the front door was chopped off by previous owner to fit a porch. Porch now removed, I'd like to restore the sill - rather than replace if possible. The sills are all painted, so colour match is not important. Could you advise on what trade I need - is this a job for a stonemason - and anything I should include in my request for quote?