The new NSC Car Share Sub-Forum may well be your friend here Notters, seeing as how anybody else in your neck of the woods and reliant on SASTA will be equally snookered.
http://www.northstandchat.com/forumdisplay.php?85-Car-sharing-to-the-Amex
It's the club - as a corporate customer - that needs to be proactively pursuing SASTA in court. Would have far more clout than an individual customer trying to do so. Utterly unbelievable that a rail company should be allowed to wreak such havoc on the community it is supposed to be serving.