I'm looking at fitting 4 general grabber 255/60 18's but worried about rubbing. Do I have to change the profile to a 55 to keep the speedo in calibration?

Hope someone can help!!

Also been offered AT's and AT2's?? Does anyone know the difference?

255-60-18's would give you a +24mm increase in rolling diameter and would inicate 50mph on the speedo whereas your actual speed would be almost 48.5mph. I've never fitted anything that wide, but several on here have and seem to be happy with them.
If you fitted 255-55-18's it would give you an almost identical rolling diameter with just -1mm from the standard 235-60-18 meaning at an indicated 50mph your actual speed would be 50.07mph.

Many seem happy with the newer AT's over the older AT2's The newer AT looks like it is styled more for lower road noise than the older more aggressive AT2 but you would have to ask those who have fitted them if you lose any off road performance.