Aftermarket parking sensors

Hi folks,

Another question for you from someone collecting their mini very soon (counting down the days).

I'm purchasing a demonstrator which doesn't have the rear parking sensors - something I would like to have. So, at the time of signing up for the car I asked the dealer how much it would cost to have the sensors fitted and he said it was expensive - can't remember how expensive, but it seemed very steep. Reason being that the whole rear bumper would need to be replaced and sprayed.

So, bearing in mind this car has the visual boost set-up, would mini-fitted parking sensors link in with the main screen or would/is it just an audible beep?

Secondly, assuming that it's just going to be too expensive, has anyone fitted aftermarket parking sensors? If so, what kind - is there any way of linking aftermarket ones to the front screen or would I be looking at an audible type possibly with a little visual light scale that you see in your rear view mirror?

I'm reasonably handy and have fitted parking sensors (the hidden ones with the metal strip that runs on the inside of the bumper) to my current ford focus.