i have the MoFi Gold Disc. it's two albums on one CD, "All Mod Cons" and "Sound Effects." i don't have original discs to compare, so i can't really comment on the sound quality. other than that, it sounds quite nice.
All Mod Cons as a more punkier edge while Sound Effects has more varied arrangements and Paul Weller is really exercising his cynical lyrical style.
i have
The Jam Greatest Hits for the longest time and it's an excellent collection of some of their songs. one could really track the band's focus from early punk songs to carefully arranged soul influenced rock. "In The City," "All Around the World," "David Watts," "Down in the Tube Station at Midnight," "Going Underground," "Eton Rifles," "Start!," "Funeral Pyre," "Town Called Malice," and "Precious" are all keepers.
oh... i would also agree that Jam fans would appreciate Gang of Four, although they are a bit more arty than The Jam. another album i could recommend in the same vein would be The Cure's debut album "Three Imaginary Boys" or the compilation album "Boys Don't Cry," which retains most of "Three Imaginary Boys" and substitutes a few album tracks for more popular singles at the time (ca. 1979).
and a tiny tidbit: the person of signed The Jam on Polydor (Chris Parry) was also the same person to sign Siouxsie and the Banshees on Polydor and also signed The Cure on his own indie label called Fiction. he also signed The Associates on Fiction.