When DH and I were looking at older rural houses, we found an awful lot of the ones on the market (most?) had two staircases, and it did seem to be something that put buyers off. It certainly put us off. However, these were usually a slightly different set up, in that you had 2 rooms and a bathroom up one staircase, and 2 rooms up another staircase at the far end of the house. We felt that for a family with 2 younger DCs, it wasn't a suitable set-up as you couldn't hear any problems in the night. It is also extremely inconvenient in the middle of the night if you have to get up, go downstairs, go through several rooms in the middle of the house and up another staircase to go to the loo.
You seem to have a better potential set up, as if only one room is on its own, as then that can be a guest room, or for a lodger, etc. On the other hand, as people said, if the bedroom doesn't have a bathroom near by, that's not going to be very appealing.
One of the things we thought was a major advantage in our house is that all the rooms are now up one staircase (after an alteration in the 1960s).
Is the house listed? If so, don't forget that you may not be able to do some of the things you're initially thinking.
Whether or not its listed, a house that age does come with a whole host of extra problems when making alterations that you won't be expecting, that will restrict your choice of builders / specialist tradespeople, and that will add substantially to the price. For example, we're currently trying to put in another bathroom. We have Listed Building Consent, but there is far less space between ceilings and floors than in a modern house, which means that we have to do the plumbing very differently and far more expensively...