Favourite not best. Just my personal favourites to watch, haven't included animations, shorts or TV movies as they belong in other lists. Dates added for those not familiar with the titles, it's not a very modern list.
1 I'm Alright Jack 1959 b&w
2 Bedazzled 1967
3 School For Scoundrels 1960 b&w
4 Steptoe & Son Ride Again 1973
5 Gumshoe 1971
6 The House In Nightmare Park 1973
7 Too Many Crooks 1959 b&w
8 A Shot In The Dark 1964
9 The Rebel 1961
10 Only Two Can Play 1962 b&w
11 Kind Hearts And Coronets 1949 b&w
12 Carry On Camping 1969
13 The Magnificent Seven Deadly Sins 1971
14 Carry On Cleo 1965
15 The Green Man 1956 b&w
16 Dad's Army 1971
17 The Early Bird 1965
18 The Return Of The Pink Panther 1975
19 The Wrong Arm Of The Law 1963 b&w
20 O Lucky Man! 1973
21 Dr Strangelove 1964 b&w
22 The Ladykillers 1955
23 Heavens Above 1963 b&w
24 Life Is Sweet 1990
25 The Man In The White Suit 1951 b&w
26 Rita, Sue & Bob Too 1987
27 Carry On Screaming 1966
28 The Lavender Hill Mob 1951 b&w
29 Hot Fuzz 2007
30 Bless This House 1972
31 The Likely Lads 1976
32 Steptoe & Son 1972
33 Educating Rita 1983
34 Alan Partridge: Alpha Papa 2013
35 Porridge 1979
36 What's New Pussycat? 1965
37 Entertaining Mr. Sloane 1969
38 Carry On Up The Khyber 1968
39 The Ghost Train 1941 b&w
40 The Naked Truth 1957 b&w
41 Up The Front 1972
42 The Wrong Box 1966
43 The Titfield Thunderbolt 1953
44 On The Beat 1962 b&w
45 The Jokers 1967
46 The Rise And Rise Of Michael Rimmer 1969
47 Loot 1970
48 The Punch & Judy Man 1963 b&w
49 The World's End 2013
50 Casino Royale 1967