It does say there "no longer available in the UK", and of course "factory built" is shorthand for the far more correct term "Type Approved Permit to Fly".
The Type approved permit list is here:
British Microlight Aircraft Association,Type Approval Data Sheets,Sub-Page There's no Jabiru.
And, yes, the engine can be a bit of a struggle at times. I think that around 5-10% of my hours are with a Jabiru engine, and about 50% of my engine failures. That said, with a good one, it's a lovely engine on the Thruster T600 Sprint, for which it seems particularly well suited.
G