Great info Neil, many thanks.
I really think that whoever now runs Elvington are taking the p*** asking 60 quid per person to tour the Hally. OK, it costs to keep it in good condition (recently had to have cash spent on re-furbishing, due to structural problems with the floor), and donations to a museum are always welcome - but that cost seems very high to me. Either make it a reasonable charge, or don't have it open at all, unless for special requests from researchers, authors, TV companies etc., as most museums would.
No doubt I'll learn more when I visit the place - don't want to 'knock' them unjustifiably at this stage.