Interestingly I've just diagnosed a similar situation for a friend (yes I do have a couple of them!) with their fridge freezer, which was going like the clappers trying to maintain temperature.
As I've written before appliances like fridges and freezer are plugged in 24/7 and once they start to lose coolant gas (most likely from the compressor) they just work longer and longer trying to maintain the correct temperature, and the longer they're working the greater your bills will be. Unless you spot the heat given off, or the fact that they seem to be operating all the time, there's no really obvious signs of a problem. But once discovered a new appliance brings with it a noticeable drop in energy consumption. This isn't something any smart meter can identify as far as I know.
But if you can monitor your electricity consumption at night when little should be working that can give a clue. -what is using all that power? Or buy a through plug meter which can measure the consumption of a single appliance - as I did, which confirmed by suspicions beyond doubt.
Its a definite exception to the "if it ain't broke don't fix it" maxim.
Current Eon Next customer, ex EDF, Zog and Symbio. Don't think dual fuel saves money and don't like smart meters. Chronologically Gifted. If I offend let me know by private message, but I’ll continue to express my opinions nonetheless.