Many thanks - I now understand my confusion. I reacted a bit too hastily and should have remembered that it is 'fydda i...' for the future in the first person
Shouldn't this be 'faswn i ddim' if it's conditional? I translated it as 'I will never eat a mouse'
See my previous reply about the two forms of the conditional.
'Faswn i ddim' would also be correct.
'I will never...' is 'Fydda i byth......
We will put this on our todo list when we have time.