I'm after a double and bash set up and I spied these:

http://www.ukbikestore.co.uk/product/56/cwths50/truvativ-hussefelt-22-rg-doublebash-chainset.html

Which get decent reviews and the price is good.

My current chainset is a Shimano FC-M442-8, Octalink Spline, and the BB is Shimano BB-ES25, Octalink spline, 68mm x 118mm

There's nothing about sizing on that link or on the Truvativ site, but does the fact I'm moving to an external BB mean sizing isn't an issue.

This is the 1st time I've swapped a crankset so I know bugger all.

The ext BB system will fit 68 and 73 mm BB so its not an issue – Some people wold suggest facing the BB shell before installing the ext bearing cups 🙂

Cheers.