The original costing included a 4X4 through Europcar and was based on paying at collection. When you added in the additional driver, etc this took the price to nearly £1,000 for the weeks rental.
However after further research it appears that a 4X4 is not required during the winter months and on that basis the cost comes down quite significantly.
Good prices were available on Avis (albeit for 2016) for an estate car which would be required given the amount of luggage (a big suitcase and camera equipment per person).
An estate car including an extra driver (so the driving can be shared) is approx £500 which works out at £125 per person if split between 4.
We would not have more than 4 people per car as it will become a bit uncomfortable. So for example, if we have 7 people then it will be 4/3 but the total cost will be split between 7.
The cost excludes all the additional insurance charges as it may be more cost effective to buy separate insurance via Insurance4CarHire, etc.