In reply to Sharp:
I would buy a rebuilt Defender but I would take along somebody who knows Defenders and I would test drive it. If the chassis has been replaced and the car built up with a mixture of parts you'd be getting nothing different from many older Defenders or 90/110s, which will have been rebuilt and repaired all through their lives. We had a 1986 ex-RAF 90 and a pal of mine who drove for the RAF pulled the service record, which ran to 27 pages of complex notes on many many refurbs, re-purposes and crash repairs it had had in its 10 year life, courtesy of the taxpayer.
As for crash safety - a Defender doesn't have airbags (they don't work in Defenders as they displace the bulkhead when they deploy) and it rather relies on just mashing through other vehicles, using them as its crumple zone. It is, as somebody else wrote, a high-speed tractor. Be prepared for high maintenance bills though if you want to keep it running nicely.