Great to see someone else headed down the same road as me
currently (still!) restoring a white & blue Perthus Pro. Its on its way back to bare metal for a respray. I'm not an expert, but for what its worth, be careful around the bottom bracket area. My frame had very minor corrosion and pitting compared to how yours appears in the photo. Reynolds 753 is extremely thin in places and 25 year old + 753 can be very delicate. Rub the frame down very carfully, especially the lower stays, then get plenty of rust treatment onto the metal. I treated the inside of my stays with a waxoil type preserver, sprayed from inside the bottom bracket shell and the drain hole in the lower stay bridge using a straw.
Hopefully someone can correct me if there is an alternative process to getting the frame restored to its former glory. Good luck and keep us posted.