Any LY or RA registered Yak was "grounded" from May 21st except that if the owner applied for a permit to fly ie on the G reg, then an exemption was issued for 3 months (likely to be extended) allowing the aircraft exemption from Articles 3 and 8 of the ANO. Any such exempted aircraft can continue to be operated on its LY or RA register effectively until it has its permit issued and it is converted to G reg.
Any Yak already on the G reg is not affected by this grounding since it has its permit already.
No need to be wary of G reg aircraft then nor indeed RA or LY aircraft provided you are aware of the costs of transter to G reg. one could for example buy a RA or LY reg aircraft and reach agreement abot the costs of transferring to the G reg...eg retention from purchase price... (just trying to be helpful).
Hope you enjoy your 52. Do yourself a favour - if you are not that familiar with the type, take a few hours with Gennady at Skytrace.
http://www.skytrace.co.uk/