Help me solve the mystery usage overnight for 3 months

I recently did a bill review and realised there was a period where I had extremely high usage last autumn. I didn’t notice as I was already making overpayments due to a billing error when first opening the account. As the issue is resolved I can’t test to discern where this came from.

the usage patterns seem like there were “pulses”. For info, I do not have heaters or water heaters/pumps etc.

any ideas as to what could have caused this?

images attached with some examples. 

( P.S. I realise this forum is for Ovo, but I couldn’t find one for octopus and since this is none account related I thought you clever people might know!)