Hi Chris
235/75 x 16 are the 'standard' 29" diameter wheels & tyres usually found on a Disco.
With a 2" lift, you can comfortably go up to 265/75 x 16 mud terrains, but (and this is where the Land Rover factor comes in).
With larger tyres and a lift - you may have to trim the arches a little (almost certainly the rear ones) and lifting MAY affect the castor on the front end.
hope this helps :)