A J Jackson's BCA 1919 - 1972 Volume III states 18 were built by Jackaroo Aircraft Ltd (Wiltshire School of Flying) and ONE was built by Rollasons
(G-APOV).
I was always under the impression G-ANZT was a Rollason machine but it would appear this is not the case, unless anyone knows otherwise.
The photos that survive of the Thruxton-built Jackaroos mostly show a kink in the turtledeck just aft of the canopy, apart from G-ANZT which has a smooth profile and a tapered fuselage. That's also the case for the confirmed Rollason-built example G-APOV, so it would certainly seem possible that, despite what Jackson says, G-ANZT was also a Rollason conversion.
Edit: This source:
http://all-aero.com/index.php/contac...xton-jackaroo-
suggests that G-ANZT was a Thruxton conversion, subsequently acquired and modified by Rollason as a precursor to carrying out their own conversion on G-APOV.
That sounds more likely.