No one has mentioned Newby Hall which is lovely. Not nearly so grand as Castle Howard. But still very worth your while. I know that it's accessible by public bus, but it would be a big hassle to get there this way.

So going anywhere over a bank holiday would be crowded ... is that what you mean?

Yes.

I think I may do this trip at another time in order to go to Krakow at this time instead. But I appreciate the comments and will certainly use them in the future.