Glad you enjoyed the read Jon, and welcome to Ten-Tenths!
I think the Group A era is quite a passion for a lot of us - me in particular the MG Metro Turbos and Rover Vitesse. Others are keen on the other marques of course -
but I don't really know why! 
Am I right in thinking your ex-Challenge Metro is one of the old Enterprise Racing entered cars? I certainly recall seeing that livery all those years ago, or is that something that you have applied more recently?