Not really an answer to your question.... but you can build a garden-room or shed with a floor plan not exceeding 15 sqm most places without planning permission ... that's 16ft × 10ft in old money and would fit a Morgan not too snugly ... you may even find a surplus wooden building that could be adapted at a push.
I seem to remember temporary garages getting a mention on here previously so hopefully someone more helpful will be along in a bit
K
