As a Doctor Who fan, it is impossible not to judge this film in comparison with the original seven-part Dalek story, so I won't really try. The positives: it is in colour, which is a huge difference. It looks better (except, oddly enough, the interior of Dr. Who's Tardis, which just looks like a film set with some machines dotted around it). The plot is tighter - it's difficult (with one exception, which I'll get to) to remember what has been cut from the original story to produce a film half its length, and some of the best bits are still there. The music is decent - not as unearthly as in the TV version, but not offensive either.
The huge difference, however, is in the performances and portrayals. Peter Cushing plays elderly slightly comical scientist Dr. Who, who keeps a time machine called 'Tardis' in his back garden, shaped like a police box for some reason. He doesn't have the grumpy gravitas of William Hartnell, but I detect some homage to his portrayal in the approach taken by Silvester McCoy. Roberta Tovey as his nine-year-old granddaughter Susie is actually rather good, and recasts Carole Anne Ford with perhaps a bit more grit.
When I first saw this on a Saturday morning repeat aged about 11, the surprise was that Ian is played by Roy Castle, who of course I knew as the presenter of the BBC children's programme Record Breakers. This was actually his second film role - he had also appeared with Peter Cushing in another Max Subotsky film with a doctor in the title (Dr. Terror's House of Horrors) earlier in 1965. Castle's Ian starts as a clown but more or less settles into the heroic sidekick to Cushing's Who by the end, probably the closest of the four main characters to the TV version (though William Russell's Ian is much brainer).
The most serious cut in the film as compared to the TV original is Barbara, Dr. Who's other grand-daughter, played by Jennie Linden. She gets almost nothing to do, except that her over-vigorous embrace of Ian sets Tardis going in the first place. (And even that is portrayed as Ian's clumsiness.) She is practically background scenery, especially when compared to Jacqueline Hill's history teacher.
Well, unless I start feeling better, I shall watch the other Cushing film later on.