Ok....bought this drive and I feel I need to share and help a little.

1. backup hd in PS3 to an external drive
2. goto Sony's website and download latest firmware onto a memory stick.
3. place memory stick in ps3 and upgrade firmware using memory stick and not over internet ( this id where I fell down as I replaced my HD first.
4. open ps3 and change drives around. ( might be an idea to not fasten screws back up so tight and not replace blue screw until you know it works).
5 start ps3 and follow instructions (insert joypad via usb, insert memory stick with firmware on, press button and then start and select)
6. firwmware upgrade process will go through now and no errors will happen.
7 continue and set up ps3 when drive is formatted and then restore back up and bosh job done.

The reason for so many errors is that when you update firmware over the net it seems to be different to the one you download from the net and gives an error hence installing the exact same firmware as in step 3.

Hope this helps oh and I ended up with 540gb even before I had restored but still more than the stock 60gb so very happy at last.

That's how you do it if you have Samsung M7 640GB 2.5 inch SATA II 8MB Cache, 5400RPM Internal Hard Drive OEM - Sony Playstation PS3 Compatible
it works