I am an spanish archaeologist and I just have return from north of Ghana, to study the women who make pottery in these area. Your guide has been of great help. We stay for a days in Bawku, in the Upper East Region. We have seen all the guestshouses of the zone, and the best, with difference, is a new one, that not appears in your guide. It is the Good Shepperd Guest House (0276261512). It’s not in the centre of town (5 minutes by car), but it’s very cleen and ordered. A double room costs 15 cedis, and it has a terrace where you can take fresh drinks. The owner is helpful and kind.
Best regards, Simon Gornés Hachero.
Bradt Ghana Travel News 
I have to second the Good Shepherd. I visit Bawku regularly and that’s where we stay. Nice rooms, good people and good price. Also, the head of security stays there too–can be handy!