had my SEGTO car around 10yrs..

ok ive not raced it all that time but i do think ours might last longer than the autograss cars.. untill you bonce it off the armco
and we do get a bit more freedom spec wise.. adustable suspension.. negative camber (lots on the passenger side) and we can do more to our engines too.. where as class 1 minis are as standard as you can get i think.. as for cages i too have seen some scary looking efforts! gotta full FIA one in mine.. dont think i'd even get in a car with just a box cage 
Your mini doesnt look too battle scarred at all - obviously not a fan of the armco!!!!
I think the best way for me to get into it would be class 1, to get a feel for things before moving up a group.
Is there anyone in the birmingham region that does class 1???
I wouldnt even get into a car with a homemade roll cage - you never know just how safe and well built they actually are.