A good choice Will and a quality battery. I dunno about the 'only' 30 Kg though, but I guess this is a bit tongue in cheek. Deep cycle batteries usually have less but thicker plates than an equivalent size auto start battery which is why they are heavier and with the thicker plates more robust (as long as they are braced correctly internally). I did a similar setup to what you're planning with this battery in my brother in laws camper van and he is very happy with it. :)
A tip, don't skimp on cable. I used 70mm (cross section area) cable on the Oka to fed the winch. Remember, you just need to run 1 wire with a VERY good chassis earth connection at either end. I ran the cable in that black crinkly split flexible conduit for extra protection. It doesn't bear thinking about the potential damage if the winch cable is damaged and shorted to the chassis when it is powered by such a large capacity supply. Chose your cable routing carefully. :)
Deano :)

