Have been having a similar problem at my parents where there was very little wireless internet upstairs making it impossible to connect a Nexus 10 tablet and not great with my laptop.
Dad unknown to me went out and bought a
Belkin range extender, which is situated upstairs on the landing and i now have full signal on both those devices, so a similar wireless access point may do the trick for you.
You could also go the home plug route, or buy a better modem/router with a more powerful wireless range.