UPDATE: Reviews section refreshed, redesigned, searchable: Go take a look
They can't fit a smart meter at the shop and I want to know how much power our Aircon is using.
Will this be of any use? If so how do I use it? 
Yes, but you'd need to clip it around the brown cable feeding the circuit that feeds the a/c - but that wouldn't be advised if it has you poking around in your consumer unit.
If you can get a reading of amps flowing through that circuit, you can use ohms law to calculate consumption.
Would I be able to use it to measure the whole shop and see how much it goes up when I turn the Aircon on?
You cant have a smart meter, but you do have a meter still? Just run a day with the air con on for half of it and off for the other half and that'll get you in the ballpark.
It should also be specified somewhere in the manual / compliance documentation.
https://www.britishgas.co.uk/heating/guides/air-conditioning-running-costs.html
"Would I be able to use it to measure the whole shop and see how much it goes up when I turn the Aircon on?"
Yes, you would need to measure how many amps are flowing through the main supply cable to the consumer unit.
Is the air con like a roof unit or portable ?
I'm no electrician but Ohms law isn't the same for ac. As above, that current clamp needs to go around some pretty chunky cables, which isn't going to be easy. Also as above, the rating plate should say what you need, and is much safer.
Understandably the engineers don't want to go anywhere near our meter. The rating plate only gives you the maximum power. Any decent air con will have variable speed drives for the compressor and fans, minimizing power vs cooling demand.
Little energy meters in DIN rail format are available to fit into a spare way in your consumer unit, you'd have to get a electrician to do that, but quick job.
(Unless your CU is similar vintage to your incomer and meter!).
Understandably the engineers don't want to go anywhere near our meter.
Engineers do what they're paid for.
My old house had something not dissimilar to that, and the electricity company fell over itself to rip it out (when I didn't really care). The solution I'd be pushing here wouldn't be clamp gauges, it's be getting the utility supplier to bring your electrics screaming into the 20th Century.
Have you changed provider ever?
You cant have a smart meter, but you do have a meter still? Just run a day with the air con on for half of it and off for the other half and that'll get you in the ballpark
Why not do this? Probably a better gauge than an instantaneous power reading since I'm sure aircon power use is much like e-bike range, it varies with how much you're sweating 😀
That's a max load/demand meter on the right, innit? Use that.
you could
BUT
the aircon will kick in and out, so you d need to log the load over time to get a fair estimation of usage. and in theory, the ircon will be working harder at different points in the day, for example, the hottest point of the day, or when you open the doors, or when you first switch it on. So, the info you are going to get from it is going to be way more basic
So
what you can get... is a bluetooth or wifi current clamp, which would allow you to log consumption over time, either similar to what you have there or something more permananet
Amazon.co.uk : bluetooth current clamp smart home
Got a fridge with a door yet or you still trying to cool the whole shop to keep some chocolate cold ?
The chocolate cabinet uses 1 kWh and gives out so much heat that the shop gets stupidly hot with the doors shut…ie when we are not there.
So interested to see what the air con actually uses as it might be cheaper to cool the whole shop at night.
