True, but there are many competent enough to accomplish this that could remove a roof and complete the mods to your specifications.
This would widen your options.
Are there other specs, like automatic, LHD, and so forth?
Defenders are very much configured to ones specific requirements.
Have talked to people who started with a ROW RHD 5 speed 5 door, and ended with a LHD "Beach Runner" with automatic that had the roll cage fitted.
Just trying to provide a solution that could end a needle in a haystack search.
Military trucks are great candidates for a conversion but hard to find in LHD. Most have the 2 piece doors and many have soft tops. The rub is they're 3 doors, not 5. A/C and auto would have to be added.
Full beach runner spec ideally would have the removable door tops.
A/C won't work as well in a soft top and prob harder to find than an auto trans in a beach runner.
You may have to be patient to find exactly what you want.