...also remember your company may have more restrictive (although badly written) SOPs about
who can carry out autolands on CAT I-only airfields!
Anyway, if we needed actual CATII/III conditions to do an autoland check, how could we do one if the aircraft had only CAT I capability until we'd done an autoland? Or are the 'conditions' you refer to in post #1 more to do with airfield protections and ILS capability, rather than Wx? If so, forgive me.
But how do you know which Cat 1 installations meet the criteria of justifiably being used to re-certify a Cat 3 a/c?
With the limited information available regarding 'suitable' a/fs, perhaps give it a go in good vis and if it plays silly b**gers prior to touchdown, disconnect the automatics, sort it out and try again somewhere else