I think where Harry has his country pad probably depends on what option they look at :
- if London is their main home:
-a larger apartment in Kensington palace, or something like York house at Saint James palace
-a smaller country cottage or such likely at Sandringham or Norfolk. To be close to William or Charles. Distance from London not such a difference as they would only use it for weekends away.
-if country is their main home
-A larger home likely at Windsor (like Andrew and Edward). Quite likely a crown lease IMO. Future kids could go to schools like Wessex kids and Yorks did. Closer to London then Sandringham or High Grove, so if they are in London on business, they aren't far from the kids if the kids are home in the country for school or simply with the nanny.
-smaller apartment at Buckingham or SJP. With room if the kids come on weekends, but mainly a place for work trips to London for the couple.