Well, thanks to all the suggestions about the mice, I might be getting ahead.
I invested in another trap - the really good quality ones (that the last party of mice took away and hid - never to be seen again) I thought it was worth another go with them - these mice might not be theives - just mice.
I also returned to using peanut butter - luckily not a favourite in our household with the two legged critters so there was plenty to spare.
Last night, when I crept downstairs to 'play' in my craft space - I discovered the trap had been set and had caught an offender. I love these easy set traps - it's baited and ready to try again.
The good news is I haven't heard any more gnawing either so perhaps the mixture of poisen and traps has killed/scared them critters enough to get them to find another home - warmer and friendlier than mine. Good riddance to them.