Unfortunately you don't have any house rules regarding use of your kitchen (or items within it) so going forward review and include these.
I think you need to sit down and have a friendly chat with your 'guests' over a cuppa. Confirm what you (hopefully) told them when you showed them around
1) that the items you have available for breakfast are only for breakfast- so not to be eaten at other times
2) if they make a mess in the kitchen they need to clear it up straight away - it's not acceptable to say they will do this later as it is a shared space
3) they shouldn't be using your personal items in the kitchen or fridge (hopefully you have given them separate cupboard space/shelf in the fridge so there can be no confusion)
4) they are not to move furniture around
5) it is not acceptable for them to lock you out of your own home
Follow up by confirming this in writing through BNB messaging so there is a record.
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