Main difference is increase in wheelbase from 110" to 130" which increases overall length from 4578mm to 5271mm - that is the rub with my garage it is only 5200 long. I would think your camper should fit a 110 with no problem anyway have a look at the Land Rover website:
Land Rover Defender 90, 110 and 130 4WD | Land Rover Australia you can dowload the latest defender brochure which will give you most info. The 130 comes standard with heavy duty suspension, steel wheels & strengthened chassis which is all optional on the 110 as part of the heavy duty pack. Wonder if they will have a good sale in the New Year, that 90" at $39,990 drive away for a 2011 model is very tempting - but I want a 110?