Hi. Can someone tell me what memory I need to buy for my Macbook 6.1 2010 model. I read that I can increase it to 8GB. I've looked on the Apple store and they only supply 4GB (4GB 1066MHz DDR3 PC3-8500) and they charge £80. I have found one on another site that is 8GB (8GB 1066MHz DDR3 PC3-8500) and they are only charging £35. Seems really weird having this much of a difference. Is this one OK to buy? Thanks.