Why don't you give the GCCF a ring and just initially ask them their advice as to what you can do in terms of possibly pursuing a complaint. At that point you don't actually have to make one - just ascertain whether you feel it is worthwhile doing so and what their advice will be?

I hope you do get this all sorted and don't let it spoil your enjoyment of the kitten.

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Kaz

For kittens, joy is for the asking and smiles are for the giving