If you flew it legally then you can log it. If you were not PIC then don't log it as such.
Prior to CPL issue I flew privately owned aircraft from grass strips, UK based club aircraft, I rented aircraft in the US and I did a bit of touring in Europe.
No questions from the CAA other than the usual mandatory cross country requirements etc. If they want to find out anything about what you have logged it's very easy for them to do so. Don't ever make anything up. (not that you suggested that)
Do something with the hours if you can. Be accurate at all times in your flying.