Parrot kits were always the go to equipment. Might be easier to fit a new stereo with bluetooth installed.

I’ve been using a Jabra BT earpiece for the last two years without any significant issues, other than it occasionally failing to re-link with the phone after paying for fuel, because I leave the phone in the car when it’s used as my satnav. It only cost me around £19. Not sure what benefits a kit in the car offers over a headset, other than two people can use it, but the headset can be paired with two phones, so it could be just left in the car, maybe on charge from an aux charger, or maybe get a BT headunit that offers phone hands free.

Not sure what benefits a kit in the car offers over a headset,

Depends if if you want to look like a taxi driver...

I bought a Bluetooth adapter that was meant for headphones, called a streambot mini for £9, and plugged it into the aux in. I use it for music and an earpiece for phone, but the streambot has a mic too for calls. You'd have to stick it on a visor or something.

Could be a cheap option if you can fit it somewhere, and it works really well for music.

Parrot as above. Depending on your needs and what you have in the existing car stereo at the moment you can have just a phone kit or phone kit with full steaming and I think some have DAB too.

Cheers folks. The bury unit in my work car has a rather substantial mic. Rightly, or wrongly, I assume that's a bit part of why the call quality is so good.