First time box + camera - comments welcome

You're not imagining it Pete, that was definitely what we call the "wriggle"! Doesn't mean anything for 100% (what does?) but it does suggest that she is sizing it up! It could be that the male was in first, and swapped places with the female - I don't have any great tit experience, but this is what tends to happen with the bluetits, and the swap can be pretty fast, and the birds quite hard to tell apart. All the action you are getting does seem quite promising, though! I'm pretty sure the GTs around my garden have just started on a second nest (getting fluff etc), so this would probably be about the right time?