Since I did the write-up I've fitted my own meter downstream of the 'official' meter because the official one runs backwards when the solar panels are running and the my system can't tell which way it is going. Its a refurbished one from Ebay often fitted by landlords to sub meter to tenants - the vendor programmed it to read only one way.. If you're lucky you might find one with a built in photo-transistor you can wire straight to the arduino. Otherwise you just tape your own photo-transistor over the LED. Your local electrician could probably fit you up if you want a completely safe job - it could be fitted downstream of your main breaker (presumably you have those over there) and be wired up in comfort. Might be a tad more complex with the funny 240v/120v split systems you employ that side of the water.