Thanks DanoT, that removes a lot of our worries and opens up our options. I will give a quick brief of what else we have found out in case other people are thinking about doing the same.
If we go for the staying in the RMR car park for say 3-4 nights a week we will get an aquatic centre pass for $135 so we are able to fill in the nights and also have access to showers.
If it doesn’t work out and RMR do kick up a fuss we have found out that KOA Camping ground offers monthly rates of $550 + HST. They said we can buy two months worth of nights and spread it out over 4 months. Doing it that way we aren’t paying for time not spent there and have access to showers when we are back in town.