Query on schengen visa

Hello there,

I am a British Citizen and my parents are visiting me from India on Family Visitor visa. They intend to visit Europe for tourism (itinerary dependent on possibility of visa). However they do not have the Schengen Visa. Is it possible for them to apply for Schengen Visa from any Schengen country consulate within UK? I have been told that certain countries (Belgium mainly) allow Schengen visa on top of UK visitor visa. Is this actually the case? The itinerary can be tailored as per the country which can allow the visa, so that is not a problem.

I seek you guidance if this is possible at all. Thanks for all the help.