Fantastic, Anthony - carry on singing! (Efo lot o hwyl!)
I'll throw in my own breakthrough. First experience speaking Welsh with someone I didn't first speak English with . I was in Wales last week visiting my daughter in Bangor and dropped into Caernarfon to pick up a certain book at Palas Print. After a quick "ti'n iawn?" exchange with the lady behind the counter, I glanced on the table next to the register and noticed a stack of "O Mam Bach." I picked up the top copy and said without thinking "dw i'n edrych am, uh, this." Hesitating, because I really had intended to look around the store, and the lady was now looking at me expectantly, I followed with "dw i'n edrych o gwmpas." She nodded her understanding and went back to her work, even though "bydda i'n edrych o gwmpas" or "dw i'n mynd i edrych o gwmpas" probably would have made more sense. After looking around for a while, I found a display of CDs and found a copy of the latest Cowbois album and asked "faint am y CD?" Fortunately, she had to scan the CD to answer, and the price appeared on the register, although I probably could have understood "naw naw deg naw" if I didn't have the visual back up
Anyway, entire visit to Palas Print and not a word of Saesneg ... except "uh, this" . I was pretty happy about that!