First of all--yes, this project has the whole trilogy available in all languages. The subs are in various formats depending on what you're looking for--SRT for software/HTPC playback and SUP for DVDs, Blu-rays, and AVCHDs. English has a couple variations just on its own--typical and SDH (hard of hearing).

The complete project (all languages/all movies/all formats) is available on MySpleen and a.b.starwars. The project package is big, because it has everything. MKVCorp said he uploaded the SRT files only to some web hosters, and you could contact him for the links. I'm a little hands-off on this project right now due to a new baby, so hopefully that will be enough to get you going.