So that g as in gwella will be ok to have around in other examples, too,
a (g)wrando, a (g)wylio, etc. - its appearance or non-appearance is a matter of choice.
...and, say, a list of names ending “and Wyn”
could end in Welsh either “a Wyn” or “ac Wyn” depending on whether you count the W of Wyn’s name as a vowel or not... mind you, I was once told off by a man named Wyn for accidentally calling him Gwyn...[ so maybe no ‘c/g’ before W in that case, I realise as I type.]
The dropping or re-instatement of the c and the g is presumably just a matter of personal preference, or a pattern I’ll pick up.
Being encouraged to pose a first question has been good, because I can now stop fixating on (and suffering from “mind gone blank” moments about) “and” as an English prompt word! Diolch yn fawr!