This is a brilliant idea. A garage that disappears into the ground. My only concern is that a "Cardok ‘mono’ lift with a flowerbed or water feature on top costs £42,000 plus VAT - plus the installation charge which varies according to ground conditions." while a "lift robust enough for another car to be parked on top and lifted up costs £48,000 plus VAT and installation".
It's not the price that bothers me, it's the fact that Joe Bloggs the plumber might come along to fix your boiler one day and park on the Cardok that isn't robust to support its weight. It won't be much fun to face a £1000 bill for a new boiler and then find a Transit van has nosedived onto your Porsche.
Explain that one to your insurance company.