No Siri audio over bluetooth

New iPhone 11 Pro Max - IOS 13.1.2 (updated today but issue was same in 13.1.1 ) - I have no siri audio over bluetooth devices. First noticed in my car when asking Siri questions (usually comes through car speakers) but when asked a question, remains completely silent but Siri animation is shown on iPhone and text is on screen (say weather etc.). Music and phone calls are ok but nothing from siri. So tested the same on Bose Mini II SoundLink - same issue - no Siri audio on speaker but does play on iPhone rather than remain silent. I noticed, whilst Siri is in action, the bluetooth icon in the bottom right of the screen, so I press this and it shows two Bose SoundLinks but as soon as I press the bluetooth icon and attempt to switch to speaker, Siri stops. Again, music and calls ok over the speaker. I've tried, unpair/pair, switch off phone, restore etc - same issue.

Just also tried my airpods - siri requests played on phone initially no through airpods. Made a phone call, came through on airpods then subsequent siri request came through on Airpods !

Some clearly not right with Bluetooth on either IOS 13 or iPhone 11 !

Have an iPhone X so going to set that up shortly and test that !