I think the bearings in my macbook fan are starting to go im starting to get a some grinding noises come from the fan, does anyone know where I can source a replacement?
Try ifixit.com for the part, and look on the site for a a guide (with photos!) to learn the installation procedure if you aren't already familiar with the process.
You should be able to buy one from your local Apple service centre. I ended up buying the fans for my MBP from a service centre and it actually cost me less than most online sources.