Just got off the phone to Craig (from Jet) who says they've been speaking to someone else who is having the same problem and it turns out they have a dodgy batch of blades for the 60a. If I lay the cutting edge of the blade on the jointer table I can see light from the other side, which is why I first thought it was a problem with the blades although the guys at the sharpening centre didn’t think so. I then received the new set from Jet and as they were they same I thought they were normal :?
Anyway Craig was very helpful and he and Nick are going to get it sorted for me - thanks guys...