I think these images appeared on the Bank of England Web site some time ago, but have been removed. However, if you just print them out as downloaded they render in life size.
The Bank of England started to produce ten shilling (50p) notes and pound notes in 1928, and the 1930 note here is that design. This did not change much until the 1963 notes came in. For more info on the history of the Bank of England and notes issue see http://www.nationmaster.com/encyclopedia/Bank-of-E ngland
The White Fiver was used between 1793 until 1957, the illustrated copy is from Peppiat's rule at the bank 1934-50. The design of all notes was changed in 1963.
Speaking entirely from very distant and very fallible memory, I think it was about the length of a current �20 note and the height of a current �50 note - slightly more square than today's notes. Now as for the white fiver, that really was an imposing note, and a lot of money!