Hi Roger,
Welcome to the forum and scheme. Good question regarding boot space. Like you and plenty others, storage Space in the back was a number one priority for the 2 cars we have had on the scheme to date.
We found that the dimensions can make a real difference. For example the Kuga and Sportage had (2017) very similar boot capacities on paper but when we visited the Kuga was narrower which caused us problems. I’d suggest going through the car scheme search filtering Large cars, estates and SUV’s. Note the acceptable boot capacity of vehicles in your price range, agree a top 3/5 and then visit them with ur mobility aids and see how they fit. That’s is what we did both times and settled on a Tuscon and more recently and Allspace.
Best of luck with your search Roger, hopefully you will find the perfect car for your family. ??