"There is, as with any radio equipment a necessity to ensure that what is transmitted is of the required standard: so not to cause interference with others and be readable by ATC, to ensure it is reliable and that the mode C transmission is accurate within the usable limits. "
The requirement for UK LAA Permit aircraft to ensure accuracy is different from EASA Certified aircraft. I don't know about microlights. Check with the microlight certifying authority for its country of registration.