Hello Dave,
I have absolutely no doubt that provided the indoor storage facility is well ventilated it will be better for your caravan. No direct sunlight to fade patterns or to denature the gel coats and paintwork, less likely to get wind damage, and out of sight.
A slightly strange down side may be that if the caravan does have a potential water leak through a body work joint of fixing, you will be less likely to know about untill you expose it rain.
Hello susan I cant help you as Idont live in your area.