S-D,
I've known about a half dozen through the companies I've worked for and I know a few in other companies now. I have sacked one - who will not get a reference from one company. Most have been employed for a year or more as their cover is often rare.
This particular situation is a "Niche" area as not many LAEs will want to work for MOD (yes, I know this isn't MOD, but...) who are widely known as low payers and:
The company is a new starter and not known/has no reputation (good or bad)
+ It's a risky job to base a sole trader's contract career on
+ Working with newcomers to the regulations
= more cash to compensate.