Found the brochure. It states:

"Featuring the renowned ROTAX engine, the CYCLONE AX3 is available with 3 engine options- on the mid range 503 engine up to five hours' flying can be comfortably achieved with the aircraft's optional 50 litre fuel capacity." (G-MYHG only had one 28.5 litre tank)

The specifications on the back page, all refer to the Rotax 503 DCDI (52 hp). So no confirmation, but I strongly suspect the other two engine options were the ROTAX 582 and 508.

The pictures in the brochure are all of the aircraft in RAF colours with no registration visible. If this was G-MYFI, I wonder why is was first registered (on 9/9/92) to a Robert George Walton of Aylebury (according to G-INFO)?

PS The total hours on G-MYFI were 2511 at 31-Dec-2008.

Rob Walton was the OC of 2409 (RAF Halton) Sqdn ATC as I mentioned at #4 and the instigator of the microlight AEF project; it was he who supplied the photo of the Tucano to UltraFlight when they asked what colour scheme was wanted.
'FI was joined in mid 1993 by GMYKA.
'FI was delivered with twin fuel tanks but if they were full, you could not (legally) fly it 2 up as you would have been over the 390kg limit.

" 'FI was delivered with twin fuel tanks but if they were full, you could not (legally) fly it 2 up as you would have been over the 390kg limit. "

I think that was why G-MYHG only had one fuel tank!

PS G-MYKA was also registered initially to Robert George Walton and later to him and Henry Alan Merriman (and in between to David Harold Amor).

As far as I recall, both AX3s were sold in late '95 or early '96; maybe Rob bought 'KA back from David Amor (don't know him); haven't been in contact with Rob since '97.

Thanks everyone for the input above, its great information and is helping me no end.