For anyone travelling to London at weekends, the Family Record Centre has microfiche copies of the calendars to wills from 1858 to 1943. They are open on Saturdays from 9.30am to 5.00pm and you don't need to book. If you are able to search the calendars yourself, it saves having to pay for searches where no will was left.
As far as I know, it is not possible to order a copy of a post 1858 will at the FRC. The address I have for postal enquiries is the Court Service, York Probate Sub-Registry, First Floor, Castle Chambers, Clifford St, York YO1 7EA.
Tel +44 (1904) 666777