I will go with the majority opinion here. Sweeney 2 definitely beats Sweeney as the best film spin-off. No silly conspiracy stories, just good old fashioned blaggers and Regan and Carter doing what they do best. Not to say that Sweeney was a bad film, just it was too far removed from the series.
The story pits our favourite coppers against a gang of ex-pat blaggers who travel back to England from Malta every time they need more funds. As a highly professional, ruthless group, they are not easy to catch and Regan finds himself under the cosh, being pressured by his boss (Nigel Hawthorn) to get a result before the inquiry is taken away from them.
Sweeney 2 is more than just an extended Sweeney episode. It's considerably stronger in terms of both violence and bad language that even the ground-breaking series never approached. The fact that in the cinema it was certified 'AA' (now 15) but has always been an X/18 rated video shows that it hasn't mellowed over time.
Although the film drags badly in the middle, this is more than compensated for by the spectacular action scenes and a tense final 25 minutes. The scene where the blaggers crash a Ford Cortina through a shop window, and leaving a police car trailing in it's wake, is an absolute corker and one of the iconic images from the film (look at the video cover if you don't believe me).
Although Sweeney 2 is very much a film for fans of the series, I'd highly recommend it to anyone who likes a good police yarn. There is definite nostalgia value of the scenes of '70's London and it's great playing 'spot the familiar TV actor' as the film included the likes of Ken Hutchinson, Brian Hall, Georgina Hale and Derrick O'Connor.