They need to be set up correctly @PollyG . It may be that your timing system is not set correctly or that you have boost enabled during the day. 
Can you tell/show us the set up? Also it’s worth checking that your meter is giving the readings the right way around - you can check this by seeing which register clocks up when you switch things on during day or night hours (peak or off peak hours)

Edit: you seem to have had a time with transposed readings a few months ago. Check the meter readings to see if this has happened again

I’m not sure how to check if they’re set up correctly or if boost is on

Are there some controls or timers?

Yes, you set the times & temp

If you had storage heaters before, you probably understand this but the basic info is -

1. The ‘output’ setting of your storage heater should be turned off at night; and also when you are out of the room or out of the house.
2. The ‘boost’ setting can be used to throw out extra warmth. But it uses expensive daytime electricity, so use all the stored heat first by opening the output fully before using boost.

As long as the timers are set correctly, it should all be ok. It’s worth just checking that the meter is reading the right way around and that the readings are what your meters say and not estimated on your bill

Great thank you