I’ve just now spoken to Motability about tinted film. They do need to give you permission and it will be added to the agreement. They’ve had no issue adding it to the agreement for us, the only requirement is it has to be fitted by a proper tax registered and accredited company. We may also be asked to remove it at the end of the lease.
We may still just go down the sun shade route as it’s cheaper but at least we have the option now