Hello Trevor,
I can appreciate the appeal of a holiday in a mobile home, but I do wonder if you have fully understood the ramifications of long term permanent dwelling.
Mobile home sites are not covered by the rent act, and thus the rental charges are basically at the whim of the site owner. The sites can make additional charges for other facilities such as grounds maintenance, extraordinary repairs, and necessary work to comply with new safety regulations, even annual gas and electrical systems checks... and so on.
In some cases the contract specifies that all gas used on the site must be purchased from the site owner.
You have already mentioned that the site you are considering requires you to replace the mobile with a new one at least every ten years. That is a considerable expense, and you must not forget that you will almost certainly be expected to sell the old one, and the site owner may charge to remove the old unit, and charge for the installation of the new one as well.
The majority of mobiles are not designed for all year round occupation, and the insulation may not be enough for winter conditions. This puts up your fuel bills
All in all, a mobile is not as cheaper option as you might think. I believe you should very carefully re-evaluate your needs and wishes and probably look for bricks and mortar. Perhaps rent or buy.