I am 5ft 10" & ride a L/20" 32" leg i still need a 400mm post in it,my mate had a M/18" & that was way to small for me so make sure you try one before you buy.
There are lots of tracks near you the numplumz boys do all the corby/oundle/kettering way,there are lots of bridleways/byways going out yarwell/wansford & around stamford.
I orderd 2 for the mayhem in 2 weeks i wanted 2 on the bars but 1 is plenty,its like the P7 torch i have but a wider beam,so i will have 1 on the bars & the torch on the lid spot on.