@djphilg I realise your post is about a year old, however, this may still be useful for other people experiencing the same issue.

If you have strange colour hues when taking photos then try using a Grey card to set the white balance when setting up at your photobooth event

I am also in the UK and have been searching for a suitable mirror, so far the option for thickness seems to be either 3 or 6mm, made from Acrylic, Polycarbonate or Glass.

Reading other posts it is recommended to use a mirror with a 70/30 light transmission, however, I seem to only be able to find UK suppliers who have 50/50.

Which spec do you end up getting and are you happy with the results?

@djphilg I realise your post is about a year old, however, this may still be useful for other people experiencing the same issue.

If you have strange colour hues when taking photos then try using a Grey card to set the white balance when setting up at your photobooth event