iOS 12 Bluetooth problems

Hi

I've just installed iOS 12 on my iPhone 7, and since I cannot get my car handsfree (a Citroen C3 - 2012) to work properly with the phone.

I can pair okay, and all seems correct but less than a minute later, the car loses communication with the phone. That is, it can see the phone as a bluetooth device but does not recognise the phone capabilities. No calls can be made, the battery level cannot be viewed and no media can be accessed. On the iPhone, the car is shown as BT RADIO, and is shown as "Connected".

If I tell the car to connect Telephone or Telephone + Media, it will connect again, but a few seconds later the same occurs.

I have tried the following,

1. Turn Bluetooth on and off on the phone.

2. Forget the connections on the car and the phone, and re-pair.

3. Reboot phone.

4. Hard reboot of phone.

5. Forget the connection on the phone and car, rename the phone and pair again.

6. Reset Network Settings.

Nothing has worked.

This all worked fine and various versions of iOS 11, so my only conclusion is that something has changed in the Bluetooth system in iOS 12.

I don't want to try to wipe my iPhone and downgrade, so I am hoping all the complaints will prompt Apple into looking at what has gone wrong and release a fix

Just as a follow-up, I also have my iPhone connected to my home DECT phones using bluetooth and this seems okay. Perhaps it is a standards issue affecting older Bluetooth systems?

If anyone has had this issue and has managed to find a work-around or fix, please let me know.

Thanks in advance.