There are basically 2 types of pumps, the type fitted outside the water tank and those fitted inside. The next move would be to find out how many gallons per minute (or litres) they pump. The most popular are Sure and Whale but there are many others available.
Unfortunately it's quite a common issue reported on Globie forums. Often it seems to be caused by the pump being activated when the tank is empty or by the bathroom tap being left open but the lever on the shower head being closed. (Each tap has a micro switch which runs the pump when the tap is opened).
This is the pump I'm carrying as a spare. Amazon product
The pump is within the freshwater tank. I've not yet had to replace mine though so hope it's the right one!
We are all sorted, the pump is working well and we have hot water yeyyyyy. We have decided that we need an isolated switch to protect the pump, in the meantime we will take the fuse out so we can’t run the pump when we have drained down. Thanks again for all your help and advice. Ginny...