The 08:03 figure is published each day in their archives at
http://markets.ft.com/research/Markets/Data-Archive?report=HR&cat=EQ
Select Equities - FTSE hourly indices - the date - and hit download.
It's only day by day though, which will be a pain if you want a lot of back data, but it is there.
How far back did you want to go anyway?
You could try using the ftse100 futures, they will have a correct open always
07/22/11 5897.00 5931.00 5865.50 5901.00 +15.00 84,661
07/21/11 5817.00 5900.00 5758.00 5886.00 +76.00 137,277
07/20/11 5773.00 5820.00 5767.00 5810.00 +42.50 109,658
07/19/11 5736.00 5778.00 5724.50 5767.50 +39.50 102,561
07/18/11 5800.00 5800.00 5697.00 5728.00 -79.00 101,623
07/15/11 5791.00 5826.00 5767.50 5807.00 +24.00 103,287
07/14/11 5799.00 5859.00 5767.00 5783.00 -39.50 111,193
07/13/11 5833.00 5875.00 5812.50 5822.50 +14.00 105,935
07/12/11 5854.00 5880.00 5754.00 5808.50 -65.50 173,460
07/11/11 5960.50 5976.50 5862.00 5874.00 -103.00 125,477
07/08/11 6032.00 6048.50 5944.00 5977.00 -59.00 123,435
07/07/11 5990.00 6049.00 5969.50 6036.00 +58.00 83,264
07/06/11 6008.00 6008.00 5936.50 5978.00 -6.00 96,740
07/05/11 5982.50 6002.50 5972.50 5984.00 -3.00 80,443
07/04/11 5965.00 5994.00 5946.50 5987.00 +12.00 47,657
07/01/11 5908.00 5983.00 5900.00 5975.00 +53.50 100,272
06/30/11 5844.00 5925.00 5834.00 5921.50 +96.50 122,821
06/29/11 5756.50 5843.00 5756.50 5825.00 +63.00 108,211
06/28/11 5707.00 5765.50 5693.50 5762.00 +56.00 100,712
06/27/11 5652.00 5720.00 5628.00 5706.00 +51.50 80,801
06/24/11 5710.00 5735.00 5640.00 5654.50 -33.00 109,621
06/23/11 5703.50 5713.50 5625.50 5687.50 -38.00 117,412
06/22/11 5734.50 5753.00 5704.50 5725.50 -23.00 87,878
thats an example
please bear in mind the ftse10 fut close at 9pm UK time