FO and any other attached personnel from other arms need not go
thru' a "formal" GCC. I know because in my reservist time, I was
attached ( almost permanently) to a certain Division. My NS
voaction was in the infantry.
By not formal GCC, I mean that you skip a lot of the combat type
training but you have to undergo familiarisation with heli -ops
(from rappelling to air guidance to whatever) and also some theory
as to what the guards would do in battalion plus ops. Depending on
the attachment job, the fam course could be 2 weeks or more.
You do not get to wear the Guards tab or beret. This is reserved
(rightly so) for those who went thru' and passed the GCC. Anyway,
you do not want to wear that .... because when it comes to IPPT,
the standard is higher.