I think you did the right thing changing frequencies, I'm suprised solent weren't more helpful initially. It can be stressful not being able to get a word in on the radio.
Last week when I was flying solo circuits (I'm still a student) the tower reported a cessna joining on base, and I was on late downwind at the time. I was looking and looking but couldn't see the damn cessna so I turned base a bit early just incase, then I tried to ask the tower about the cessnas position but the radio was busy. There was some guy on the radio recieving a long IFR clearance and 4 times he wouldn't read back correctly, so the controller kept repeating it, it was stressful not being able to ask the tower. Eventually I saw the cessna flying parrallel to me on a wider base leg, I wasn't sure if they'd seen me and I didn't want them to turn final into my path, still I couldn't inform the tower. In the end once I'd turned final I managed to tell the tower I was visual, just so the cessna knew where I was, as they were probably expecting to join infront of me. But it was very frustrating not being able to make radio contact.