"Don't get anything called just "Nations", it could well have SF and in any case you'd want to upgrade straight away.
If you bought Trackmania United (and why wouldn't you?)"
Yep, the original NATIONS does indeed include Starforce whereas the new one thankfully doesn't. It's a great freebie.
However, regarding the "why wouldn't you?" comment regarding Trackmania United, well...because it DOES contain Starforce ! (only a "light" version apparently, on both the retail and downloadable versions, but ANY form of Starforce is dodgy and risky as far as I'm concerned, so your post seems a little bit contradictory in that respect).
That only concerns the original release of Trackmania United though.
If you now decide to buy the downloadable version of Trackmania United bundled with the FOREVER add-on, it no longer includes Starforce.
Unfortunately it costs £19.99.
You can buy a brand new copy of Trackmania United in the shops (with Starforce) for about £6.99, and the FOREVER expansion is a free download, so £19.99 seems a bit steep.
I'm going to wait until the retail version of UNITED FOREVER (without Starforce) hits the shops (it's coming soon apparently), and I'll no doubt be able to pick up a copy for under a tenner within a few weeks of release (great game in short bursts I'm sure, but not worth risking £19.99 on for me).