Hi Neilw, I have a Koga Miyata World Traveller I am thinking of selling but this may not suit as it is 26'' wheels (by far the best bet if you are getting off the beaten track). Will carry the world and your mother-in-law without any problems on and off the beaten track. It is medium size, though at 5'9'' I am glad I did not get the larger size - so should suit anyone 5'7" to 6'2".
2007 model and I have done 3 long hauls on it without any issues. I paid £1,300 for it so cannot sell for silly money as it is still in perfect condition.
John.