I've just checked my course photo when I started training on Provost T1s at Tern Hill.
One of our number was a National Service pilot inasmuch as he was trained to 'wings' standard and then continued with a reserve squadron after his two years. Despite that he was not able to wear wings, possibly on the basis of having to serve six months on a squadron. I had reason to look at his log book and it had a few entries on Harvards after his training.
He had to do Basic and Advanced before he got his wings back again.