Thanks @SpideyMom I would appreciate you asking your sister.
I'm sorry you're in a similar position. It's such a unique time isn't it and my ex has been vague to say the least in saying 'not working' instead of furloughed.
When I looked at the CMS website it says the changes to report are as follows... I've copied and pasted it...
If your circumstances have changed for one of the following reasons, call us straightaway. We can only deal with these changes if you report them by phone so please do not report them online.
• If you have lost your job
• If you are temporarily receiving no income while you are self-isolating during the outbreak of Coronavirus
• If you are temporarily receiving statutory sick pay during the outbreak of Coronavirus
• If child maintenance should no longer be paid because of a change in circumstances
• If you are adopting a child
• If you are reporting a bereavement
We cannot accept details of any other changes by phone. You can report them by registering or logging into your self-service account instead. Visit www.gov.uk/coronavirus for the latest advice about Coronavirus.
From the reasons listed above, none of these seem to apply to people who've been furloughed... my ex works as a salesman so I imagine he has a basic and then earns commission. All I can assume is he'll have been furloughed on his basic. The frustrating thing is I can only take his word for this.
I'll await to hear what your sister knows. Thank you again 