No. Sky digiboxes DO NOT output SVHS via the scart socket. Sky+ boxes DO output SVHS. A cheap £8 convertor will not work, as the pins are not connected properly inside the digibox. All the cheap convertors do is change the format/style of the various connectors on a scart socket, but all pins on the scart have to work in the first place for this to be of use.
The projector surely has a yellow phono "composite" input that could be used?