AFAIK every European CAA treats charts as a moneymaking project, which is why they are not in the AIP. The only stuff in the AIP is what each country is obliged to release under ICAO obligations, and it doesn't need to be particularly usable by pilots (ref: most AIP approach charts).
Greece does not publish VFR charts as a whole so the 1998 ONC is still the last one
There are some fragments e.g. the Athens TMA and its VFR routes in the AIP, which is not online and has to be purchased. A lot of people use the Jepp IFR enroute charts which are OK, especially if you mark up the CAS from those onto the ONC chart.
The basic issue with VFR charts is copyright. Jepp have done VFR charts for most of Europe but they are not cheap - about 300 euros for the whole lot. They have appeared on P2P in Oziexplorer format, presumably from a scanned job, and same has happened to the UK VFR charts, but this is obviously not a commercial solution.
There is no real unified solution to this. I see some products coming out with national "ICAO" charts, which are probably cheaper to license than the Jepp ones.