Hi all, thanks for the comments and advice.
I'm going to view this car on Wednesday this week (it is still available). As advised I'm looking for someone with experience of Morgans of this age to come along and cast a critical eye. I'll be asking to get the car on a ramp to look underneath so hopefully no crawling around on the floor! Otherwise I'll be trusting on the reputation of the dealership and my experience of old cars in general.