I've done a little more investigation into this engine noise.
The noise is present when removing my foot off the accelerator (at speed, eg changing gears quickly) and it is more of a whoosing noise, as if air is being sucked into or through a tube.
Thanks for that will take a look. But after further driving the noise is only made when I am accellerating and physically removing my foot off the accellerator.
Here we go then, just been out to look if I have any broken cracked pipes as suggested by JFL. Upon opening the bonnet I noticed a strong smell of exhaust fumes. Went and had a look at what was coming out of the exhaust and got nothing. Absolutely nothing coming through, however I can't get underneath at the moment to check where it has come apart. Guess the garage is my next port of call.