Either:-
(a) Class 1 medical + CPL + FI + valid microlight rating.
or
(b) NPPL Medical + PPL + FI(microlights)
The Texan isn't currently approved in the UK by the way, but the CT is.
The syllabus for the NPPL(M) is online at
http://www.nppl.uk.com/
More on the microlight instructor qualification
here
G