They don't have to be solo to be PIC. The key is that for an IR you need 50 hours PIC cross country. I would bet you're all set.
Count the hours you did after your PPL was issued. Talk to your flightschool. You're entitled to log those hours as PIC. You are a licensed private pilot and the fact that they didn't let you fly more solo, is not a matter of legality, but rather airplane ownership. If you weren't ready to command an SEP-L, then you wouldn't have a PPL.
But here's the thing you'll need to clarify. The requirement says those 50 hours have to be cross country. The regulations aren't precise about whether a cross country flight requires to have different departure and destination aerodromes. Some parts of the regulations refer to them as any flight more than 3nm away from the departure AD. Some other regulations refer to them as any flight from a point of departure to a point of arrival using standard navigation techniques, without saying if departure and arrival must be two different places. People doing hour blocks usually plan flights with some full stops in between departure and arrival from and to home-base... I've asked about this a million times, and nobody's ever given me a definitive answer.