Good attempts here and by email. No-one got 100% (not even me who got a question wrong).
Which is the only Ken Russell film to have a sequel? It was not directed by Ken.Whore 2 (it is not very good and only vaguely related to Whore)
The Rainbow directed by Ken is a sequel (actually prequal) to Women in Love, both novels by D.H. Lawrence
Which film of his is one of the few non-Beatles films to include a Beatles song (not a cover)?Billion Dollar Brain
Which film includes a homage to Eisenstein’s Alexander Nevsky?Billion Dollar Brain
The connection between Russell, Godard and Sturridge?The compilation film Aria. The best segments are by these three. Disappointing segments were by Jarman and Roeg
Which film has a script based on a translation by his then wife Vivian?Salome's Last Dance. Oscar Wilde wrote the play Salome in French to (unsuccessfully) avoid the censors who forbad depiction of biblical scenes on stage
Which film star has a role in Altered States aged five?Drew Barrymore
Which ballet dancer appears in five Russell films as well as two television films?Christopher Gable, notably as Fenby in Song of Summer. He was principal dancer at the Royal Ballet
The connection between Polanski’s Cul de Sac and French Dressing?Error in the question: T
he connection between Polanski’s Cul de Sac and Billion Dollar Brain?Francois Dorleac appears in both. B$B was her last film, she died before the premiere aged 25
Which film was later adapted into 3D?Gothic (very bad in 3D)
Which film includes a homage to Death in Venice?Mahler
Which actor has appeared in the most Russell films (excluding television films): Oliver Reed/ Glenda Jackson/ Murray Melvin/ Christopher Gable / Georgina Hale?Glenda Jackson, Oliver Reed and Christopher Gable with 5 each.
If you include TV it becomes
Oliver Reed 5 + 4 + 1 Radio
Glenda Jackson 5 + 1
Murray Melvin 3 + 4
Christopher Gable 5 + 2
Georgina Hale 5 + 1