Hey, sort of the right area but the general area below would yield more view and answers.
You can go to volvo and get charged a small fortune for the volvo kit, or you can go down the route you suggested. Personally, you can get the kits off eBay for £20 max with good instructions and they will come in the cars colour if you buy the right ones. Easy to fit as well.
I expect you’d get some fitted at
https://www.smartinstallation.co.uk/parking-sensors
Which is based in Leicester as I believe you are?