We have been touring Georgian houses around GB and have to rate the experience at Fairfax House not worth your money or hassle. There's load more to do in York. Went on Monday because I wanted to take advantage of the guided tour. Not a pleasant experience as the guide rushed us through, refused to answer questions if he didn't feel like it (You can buy a book downstairs we wrote about our furniture if you wish to know what that desk is for, Madam!) and got offended when I looked through the guide book I bought to see if I could learn there's anymore information about the room he was rushing us through. Turned out if we want to look around we would need to come back another day. Not sure why they offered the tour separately this way. The guidebook was mainly about the renovation process so be aware, unless you're into learning about it.
The whole visit was so unpleasant and so unlike the other Georgian Houses we've toured (Edinburg, Bath are two of the best!) I would not recommend anyone with an interest in Georgian period make a special trip to York for this, or if you do visit, don't bother with the tours. Didn't bring children and glad I didn't, despite 16 and under free.