XT triple.
buy new from wherever (I bought a new set from Wiggle on Sunday for £97.50 delivered) then remove the rings and sell (I’ve just sold two unused sets of XT rings for £35 a set).
this leaves you with a brand new set of XT cranks with the right chainline for single ring including new bottom bracket for £62.50.
do this twice (which i did as i bought a silver set of cranks and then realised that i wanted black) and by the time everything has been sold (i had no problems with selling the chainrings @ £35 and the cranks for £75, as most people get greedy and ask for more) and it ends up costing you £50 all in.
I was quite tempted to go down the XTR route as there is a lady on pinkbike who has a brand new set of 160mm triple XTR cranks inc. bottom bracket and rings for £200, but figures that i was already on to a good thing with the XT cranks @ £50 and after selling the XTR rings, I would probably be in at closer to £135.
just waiting for my crank skins to arrive from the US now so i have a fighting chance of my shiny black cranks staying that way.