A320 Captain reported returning to the gate after noting high fuel temperatures during taxi.

Narrative

We were dealing with an APU not doing a great job of cooling the aircraft while on the ground in ZZZ. The cockpit temperature never got below 90 and the cabin remained at 84/82. Knowing we had a 20 minute flight back to ZZZ1; we elected to continue. Performance mandated we take off in the opposite direction in ZZZ using runway XX. The push was delayed 10 minutes for ground traffic out to runway XX. Startup and taxi went normally but the interior started heating up after engine start. Temps hovered at 98 in the cockpit and 88/84 in the cabin. We were hoping to hustle because once airborne the plane would start cooling off. Ground told us takeoff would be delayed at least 20 minutes due to arriving and departing traffic.After a 10 minute sit waiting for takeoff; we got an Master Caution Light and ECAM message stating a fuel overheat condition in the left wingtip fuel tank. The temperature was 57 C and in less than 20 seconds it climbed to and hit 72 C. We accomplished the ECAM actions shutting down the left generator and left engine. We were now obligated to return to the gate.We asked for a taxi back but ground stated we could not taxi back for at least 20 minutes. In the meantime the right wingtip fuel was overheating hitting about 58 C when we made the decision to advise ATC to gain traffic priority. We got an immediate back taxi down the runway and returned to our pad location. We accomplished the remaining ECAM actions once parked; shutting down the right generator and right engine. The temp reached 68C in the right tank at shutdown. Cabin air temps remained at the previous highs of 98/88/84 during the whole incident.I exited the cockpit and asked the passengers to quickly but orderly depart the aircraft down the front and rear airstairs. We were concerned about how high the temperatures actually went in the fuel tanks. Ground fire fighting crews rolled and monitored the fuel tank temperatures. The passengers were calm and the exit was swift and orderly. I asked my inflight crew to go with the passengers and had my first officer manage the arriving staff while I cleaned up the remaining checklist items and shut down the aircraft.