Col, I can add a few thoughts for your consideration.
I am slightly lighter than you at 70-72kg (depending on how many mince pies i've eaten

), and I have a XFire102. This board works as my "big" light wind board, and I can get planing with my 7.7 and 38cm fin in the same wind that I can get planing on my 130L Carve. The width and light weight of the XFire helps. The 102 XFire also is comfortable in the Swan chop powered up with a 6.0 and a smaller fin (32-34). The relativley narrow tail I think helps with control. Having said that, once it is windy enough for the 6.0 I am usually happier on my 85L Sonic.
What does this mean for your board selection? For a 1 board quiver I would seriously consider a XFire 90. Best bet is to demo a 90 and a 102 (if possible demo the 90 in light wind, and the 102 in a strong breeze to better assess which one will cover your required wind range). The 90 could be the go if you want to get the best of the stronger sea breezes, or the 102 if you don't want to miss lighter wind sessions. To my thinking the 112 might be a bit big as a 1 board option, but would certainly get you going on more marginal days - with the compromise that it might become a bit of a handful on the windier days.
Hope that is useful feedback! Jesper may also have some thoughts.