Is this a different whistle than you were talking about in the lounge thread about your car sounding like a supercharged one?

no that thread is a spoof of this one.

But the one in 'general chat' looks to be close to this one.

They're completely different, I think my L36 has a desire to be an L67!

When I get the time I'll check out what the whistle is.

It also does it when I use the Cruise control to speed up, so it has to be from a hole, there's not really any other explanation...

check for vacuum leaks around the cruise control actuator... that might be it... possibly

How would there be a hole, was it my fault? How do I prevent from happening again if it is?

Check for hose leaks or rotten hoses to the actuator motor, which is controlled by vacuum like TL said. The CC motor is connected to the TB by a cable, so follow the cable to find the CC motor. Sometimes hoses just wear out and other than replacing them all, there's not much you can do to prevent it.