I was looking at the fast track security thing recently. According to the oneworld website HEL is one of the airports where OWEs are entitled to use the fast track security. So even thought BA don't pay for it for SCHs and GCHs, it seems as a GCH you would be allowed to use it.
I didn't know this last time so didn't try, but will try and see what happens next time I am there in May.
See the link here
http://www.oneworld.com/fast-track