You'll answer your own question when those swatch books arive and you see that yes, compared side-by-side, there really is that drastic a difference between that ink formula (not strictly a 'colour') printed on coated and uncoated. You won't get anywhere very close, visually, to 2745 C on an uncoated stock. Quite often it's better to spec different spot colours for different stocks, though most designers seem to prefer not to (or worse, use 'C' swatches for everything and expect them to print that way).
But this isn't new to the CS6 swatch libraries. They might have been updated a little, but the two 2745 swatches look pretty much the same in CS4. Maybe you didn't have spot colours set to use Lab values in your previous version.
Many thanks for your post. Talk about timing - the swatch books have just arrived, and yes, it confirms your diagnosis - spot on. I don't have access to previous Pantone books prior to the 'plus' series to see what it looks like in there, but it's not too far off my screen rep looking at these books.
Regarding CS6 swatches compared to CS4, I understand that Adobe has changed the default method of basing them on CMYK to use LAB now, from what I've Googled since. I always used the default settings (pleading ignorance now over managing my colour workflow), so that's not something I'd of changed to LAB. Looking at the swatches now based on LAB it's much closer to the book, which is obviously great.
Finally, what 'Suite Colour Settings' would you set to synchronize over all apps - I'm set on 'Europe Prepress 3' given that all my work is print based.
Thanks loads for your help, it's greatly appreciated Danny.