Im looking to respray my car, and im picking out colours...

The official BMW website features a Laguna Seca Blue (Metalic) available on the M3 and appears to be a light blue.

The BMW World website features this car http://www.bmwworld.com/media/wallpaper/m3_blue.htm

But that blue is vibrant and does not appear to be metalic.

The paint code supplied by BMW World is 448, and this concurs with my paint suppliers code.

A search for more pictures found a Laguna Seca Blue that was alot closer to the one pictured on the BMW website. See below link.
http://www.m3supercar.com/e46buyersguide4.html

Can someone please confirm for me what that colour on the M3 from BMW world really is.

Thanks,
Brent.

Doesn't exist, it wasn't a production color, it was only used for advertising. Same concept as chrome silver, a ~10k hand-sprayed 4+ layer paint that all of the new BMWs featured at national auto shows usually carry.