Testing Loop Energy Monitor
After going through all the options earlier, I eventually went for the one I'd thought about months ago (I very much follow the not-actually a Churchill quote but should be in my decision making).
Sent off for my free Loop trial, 45 days to test the device and then you can either pay a one off costs (around £50) or pay monthly to keep using it. So far the graphs look pretty but need more data to see anything useful. No way to export the data out either at present, but an API is "in the works".