Looking for Motorhome swap in UK from NZ

We are planning a possible motorhome swap to visit the UK (first time!) and a bit of Europe for about 6-8 weeks from mid June to mid August 2014 (If anybody prefers a different time in NZ, that would be fine with us) 

We have read the NZ magazine of our Motorhome Association and found very good feedback about the members’ experience by becoming a member of your Club 

We  would like to get advice about timing, licence requirements for a UK motorhome > 3.5 ton, insurance and whether anybody is interested in a motorhome swap in NZ 

We have a four year old Iveco 6.5 ton, 8 m, certified self-contained motorhome (requires heavy vehicle licence, one up from the car licence – build for two, but can sleep four – we live in it permanently, semi-retired couple and would love to swap for something similar or smaller? 

Advice please how to plan and organise this to cover all possible hick-ups. Our van’s insurance will cover the visitors to NZ, small excess fee and permission necessary from our insurer