Bitstring , from the wonderful person Rick said
You want RPI data (probably) .. although 'cost of living' depends on how you live (i.e. do you have a mortgage). The government site has several you can choose from - last release was on 12 October, so look for 'consumer prices index' on 12 October here:
formatting link
If that doesn't go back far enough, email me and I'll send you an excel spreadsheet with RPI data back through 1976. Ah, b&gger it, have it in (wide) txt format:
1976 1977 1978 1979 1980 1981 1982 1983
1984 1985 1986 1987 1988 1989 1990 1991 1992
1993 1994 1995 1996 1997 1998 1999 2000 2001
2002 2003 2004 Jan 37.49 43.70 48.04 52.52 62.18 70.29 78.73 82.61
86.84 91.20 96.25 100.0 103.3 111.0 119.5 130.2 135.6
137.9 141.3 146.0 150.2 154.4 159.5 163.4 166.6 171.1
173.3 178.4 183.1 Feb 37.97 44.13 48.31 52.95 63.07 70.93 78.76 82.97
87.20 91.94 96.60 100.4 103.7 111.8 120.2 130.9 136.3
138.8 142.1 146.9 150.9 155.0 160.3 163.7 167.5 172.0
173.8 179.3 183.8 Mar 38.17 44.56 48.62 53.38 63.93 71.99 79.44 83.12
87.48 92.80 96.73 100.6 104.1 112.3 121.4 131.4 136.7
139.3 142.5 147.5 151.5 155.4 160.8 164.1 168.4 172.2
174.5 179.9 184.6 Apr 38.91 45.70 49.33 54.30 66.11 74.07 81.04 84.28
88.64 94.78 97.67 101.8 105.8 114.3 125.1 133.1 138.8
140.6 144.2 149.0 152.6 156.3 162.6 165.2 170.1 173.1
175.7 181.2 185.7 May 39.34 46.06 49.61 54.73 66.72 74.55 81.62 84.64
88.97 95.21 97.85 101.9 106.2 115.0 126.2 133.5 139.3
141.1 144.7 149.6 152.9 156.9 163.5 165.6 170.7 174.2
176.2 181.5 186.5 Jun 39.54 46.54 49.99 55.67 67.35 74.98 81.85 84.84
89.20 95.41 97.79 101.9 106.6 115.4 126.7 134.1 139.3
141.0 144.7 149.8 153.0 157.5 163.4 165.6 171.1 174.4
176.2 181.3 186.8 Jul 39.62 46.59 50.22 58.07 67.91 75.31 81.88 85.30
89.10 95.23 97.52 101.8 106.7 115.5 126.8 133.8 138.8
140.7 144.0 149.1 152.4 157.5 163.0 165.1 170.5 173.3
175.9 181.3 186.8 Aug 40.18 46.82 50.54 58.53 68.06 75.87 81.90 85.68
89.94 95.49 97.82 102.1 107.9 115.8 128.1 134.1 138.9
141.3 144.7 149.9 153.1 158.5 163.7 165.5 170.5 174.0
176.4 181.6 187.4 Sep 40.71 47.07 50.75 59.11 68.49 76.30 81.85 86.06
90.11 95.44 98.30 102.4 108.4 116.6 129.3 134.6 139.4
141.9 145.0 150.6 153.8 159.3 164.4 166.2 171.7 174.6
177.6 182.5 188.1 Oct 41.44 47.27 50.98 59.72 68.92 76.98 82.26 86.36
90.67 95.59 98.45 102.9 109.5 117.5 130.3 135.1 139.9
141.8 145.2 149.8 153.8 159.5 164.5 166.5 171.6 174.3
177.9 182.6 Nov 42.03 47.50 51.33 60.25 69.48 77.79 82.66 86.67
90.95 95.92 99.29 103.4 110.0 118.5 130.0 135.6 139.7
141.6 145.3 149.8 153.9 159.6 164.4 166.7 172.1 173.6
178.2 182.7 Dec 42.59 47.76 51.76 60.68 69.86 78.28 82.51 86.89
90.87 96.05 99.62 103.3 110.3 118.8 129.9 135.7 139.2
141.9 146.0 150.7 154.4 160.0 164.4 167.3 172.2 173.4
178.5 183.5
hint: you need to set your right margin WAY over there-> to see the table properly.