Hi Gaz,
There are several system on the market, Kufatec and Maxhaust.
I have the later one, and I install them too here in France.
The sound is pretty good, you control it via an App (Android ans IOS), once set to your liking you don't touch the App any more, you just use the speed adjusting cruise control button on the left of the wheel.
You can cut the sound of altogether on the Mway, it's what I do. (for a quieter ride)
The system is however not plug and play (none are), you need to be a fairly good DIY man, either to dismantle the original connector to parse in the Canbus wiring, or to cut it and solder the new module Canbus in.
If it is prior to 2016 the module is in the boot after it is under the front left seat, for LHD cars, for RHD ones it should be the same but can't guaranty.
If you're interested in doing it yourself, I still have 2 in stock. (I can assist you or your installer remotely via Whatsapp, I've done it for an English member already)
This is the unit.
Active Sound, Soundbooster, Soundmodul, High and Deep Speaker for MASERATI GHIBLI (M157) 2013-... Ghibli 3.0 D, 275PS/202kW, 2987ccm
www.maxhaust.com
send me a PM if you're interested (better price)