I thought i should give you an experience i suffer from which may help?

50% of the time i switch my lathe on i trip the main breaker. This is because of the in rush of current to the 2kw inverter controlling the lathe (tested this by switching inverter on before applying breaker and all ok).

When the lathe is running it will trip out the main breaker, took ages to work out why. The reason for this is because the oven is on in the house, when the temp on the oven gets to a certain point the temperature control causes an earth problem (expansion). A known issue with a lot of ovens if you google it

To fix my issue when i get time is to run new armored cable i bought to the workshop. I shall connect it to a type 'D' RCBO to the none RCD side of the consumer unit in the house and use type'D' mcb's in the consumer unit of the workshop.

If the misses is really lucky i might get a new temp control for the cooker ;-)

In short look for other items that are on for a while as the problem may not happen until warmed up? i appreciate what your going through as it too was a long time for me to find my issue. For the time being i can work round it so no rush.