Fitting Factory VT Fog Lights

Hey Guys,
I have recently received some Factory Fog Lights to install to my series 2 Acclaim. I have the bezels for them too, however i cant find any bumpers for sale to suit (Calais/SS) So i am thinking about cutting into my current one, However i am not sure the best way to do so and how to make sure that it will all line up straight.

Any Help would be Greatly Appreciated.

Thanks Guys,
DaLyrics6