The first thing I'd do is hand in your notice period. I'm in the same predicament as you and they want a 1 year notice to leave. So I sent them the notice and thought to myself that its given me a year to find a replacement, and worse case scenario (which I know won't happen), i'll just stick with them for another year.
You're right that the software is extremely outdated and their promise of updating just is an expensive overkill with nothing to show for.
I'm looking down the route of some of the other companies mentioned here, and integration with Wonde would be amazing to reduce admin time.
Good luck and it would be interesting how some of the others have done with the newer systems they've adopted.