The only English loanwords I've seen so far are beic and car.
This course also includes "Sori" though, which isn't really a Welsh word. I've never heard it in Welsh. What we typically say is "Mae'n ddrwg gen i" (It's bad unto me), however that's not quite the same in usage as "sorry" which can be purely sympathetic.
There is also mac which is mab in Welsh & Breton ("son"), ainm and enw (is it right?) meaning "name", dubh and du ("black"), etc... Q-Celtic and P-Celtic languages are distantly related, but still related!