Aim Far,
I used to instruct on the SIAI MARCHETTI SF 260 while on contract to the Singapore Air Force. From what I remember of it, it would meet most of your requirements. I am not sure of its availability in the UK and I have no idea of its cost. It does have a stick, tricycle undercarriage, is fully aerobatic (although being carburated its negative G time is limited), and cruises at 145kts+ (indicated). If you want to, it can do a loop from the cruise. We used it only as a two seat trainer but I understand that it can take four. Not too sure about the range, but 600+ miles should easily be possible.
Hope this helps.