Nothing particularly wrong with the AX2000, although if you don't need it to be Type Approved, I'd look at the X'Air which is a better sorted development of the same family.
The HKS700E is tiny, gutless, and unreliable with poor spares availability. Really, the 2-stroke 582 is a much less problematic engine. On the X'Air, I'd rather have a 582 or Jabiru.
For any microlight, before you buy - pay a BMAA inspector to go over the aeroplane with you. If you're taking a quick initial look, download the BMAA Type Approval Data Sheet (or Homebuilt Aircraft Data Sheet as applicable) and permit inspection checklist and use those to go over it. Very importantly, ensure he puts a Bettsometer on the wing and gives you an honest estimate of how many years until the sails will need replacing.
Have your inspector go over the paperwork as well, as paperwork not in order can cost you a lot of aggro.
Spares for the AX3 and AX2000 (including new sails) are available from P&M aviation in Rochdale, who are successor to Pegasus / Solar Wings who manufactured the aeroplane originally. Spares for Rotax and Jabiru engines are readily available from their importers. I suspect that HKS spares could prove problematic.
G