I am sorry to say as an ex member of HM Army, that some of my former workmates are of the very thick variety, and whilst I don't condone their attitude some particularly infantry regiments take a VERY dim view of Civilians wearing their regimental colours. Have heard of people having ties taken from because they are not entitled to wear the brigade of guards tie. Some of the more moronic ones are not above coming to blows over it, DON'T ever wear a plain maroon one as that is the parachute regiment and they have been known to start fights just because someone is wearing a maroon sweatshirt.

I don't know what regiment that belt is for but if you wear it just be aware that you will upset someone, it just depends how much.
Its quite bizarre as nobody would raise a problem with wearing the regimental tartan but, try the stable belt or regimental tie or blazer badge and they will raise hell.