If looking for a DIY build using a second-hand vehicle, you can't do much better than buying an old Emergency Ambulance.

Due to their original requirements, vehicles come with powerful engines, uprated gearboxes, suspension, and far improved braking systems. They are usually well insulated for sound and heat, and are already fitted with rear heaters. Due to their need to power items such as Incubators and Defibrillators, they have the wiring installed and heavy duty batteries.

There are a few specialist companies that sell used emergency vehicles across the country, who buy whole fleets of vehicles once the Ambulance Services replace them, and can be purchased quite cheaply, and some are sold by auction.