I saw a YouTube video recently where an inexpensive Single DIN head unit with Apple CarPlay was installed in an XJS. Though I would enjoy Apple CarPlay in my daily driver, my preference for the XJS would be for the original radio to simply utilize bluetooth for music in some seamless way. I tried one of the cigar lighter fm transmitter bluetooth units, and found it lacking, plus I didn't like the look of it sticking out of the lighter socket. The XJS is becoming a classic car, and it should look period correct.

I found a very inexpensive and quick install solution:

UNI-BL-FM Band Expander

Which I was able to order on eBay:

https://www.ebay.com/itm/116169677972

It could easily be cheaper I suppose, but it is a nice solution for my purposes. The install is pretty straight forward and easy. You pull out the headunit and use a tap Scotchlock type connector on the antenna power out wire to get 12v, unplug the antenna coax from the headunit and plug it into the female plug of the bluetooth unit and plug the male end into the headunit. If you remove the passenger console side panel, you can hide everything in that area so it doesn't interfere with putting the headunit back in. It even has a volume up and down to calibrate the volume and not overdrive the original radio's amp.

It works a treat, with one minor but ignorable annoyance. There is an announcement when you first turn the radio on that bluetooth is active and another that it has connected. Which when I first tested the unit, I said to myself, 'why is this Chinese woman yelling at me?'. However, once I got the volume properly calibrated it is now less shouty. So far, my iPhone has not failed to connect right away, and sound quality is much better than the fm transmitter cigar plug type. You still use one of two FM frequencies to set a preset, but because it is hardwired the sound is better.