FTL Software
There is a new company just started who mail-shot last week.
One Track Software
Their systems are aimed at the bizjet market, rather than airline, so no massive hardware costs, just stick it on your pc. They're offering a stand-alone crewing program if you don't want to go the whole hog and ditch your spreadsheets!
On the CAA approved software question...I don't think any software needs to be 'approved' as such, as it's only record keeping and so no different to spreadsheets or pen & paper. As long as your FOI gets to see the end result, on printed pages, I wouldn't have thought he'd care how it was tracked...as long as it was correct.
In fact, I would have thought that going computerised would help with the company Quality Systems so your FOI would probably give any software based tracking method the thumbs up