That's quite a daily commute!
I would still be tempted to get the battery checked, are you a member of the AA / RAC or such like? might be worth a phone call, and explain about your intermittent park brake problem.
Couldn't advise you on whether to take to a Jag Dealer or not, but if starting a new job, I would fully charge the battery a couple of days before you start, and test it each day, to see if the problem reappears, may just save you an embarrassing first day in the new job!
Steve