Hi there,
I know guys that have done both (worked as FI's and had aviation-related ground jobs - even one who was a hostie) and moved into the airlines over the last 12 months.
My own preference would be to go the FI route. For one, you will be flying (far more fun than a desk job, even on a bad day), keeping current and probably have the better chance of later employment.
Also, BA CitiExpress haven't to my knowledge taken any newbies since at least summer 2002 when they last interviewed for vacancies, and I still know one guy who has been in their hold pool since then without any luck. I wouldn't waste my time there hoping to get a job with them, as I reckon they are just about the least likely operator to recruit. If you want a ground job, at least choose someone with better employment prospects.
Good luck though.