Groups are nowhere near the hassle you suggest, provided you get to know the members and have decent guidelines/rules.
Even with six members we've never had an availability problem.
£20k would buy you into an excellent aeroplane and the hefty bills you can expect taste a little bit better when they're divided six ways.
However with out knowing more about your aviation plans ( leisure/hour building / commercial/LAA)) it's difficult to make any further suggestions.
If you do go the sole ownership way, get as many rides in different types before you take the plunge: It's a buyer's market at present but if you end up buying a dud you'll be a long time shifting it.
Good luck
Cusco
EDIT Missed your Jabiru suggestion: Have you flown in one: A guy at our strip got rid of his as he was tired of getting bounced around in hot weather........