Revalue foreign bank accounts not picking up correct rate

I am working on accounts for the company with multiple currencies.

I have used CB FX revaluation to translate balances on EURO bank accounts to GBP.

While checking and comparing FX rates provided by CB, I compared are produced after revaluation ( balance of 3,368.80 EURO after revaluation was 2,589.46 GBP), to rate on 31/10/2012 used by CB for daily transactions (sales/purchase inv, etc).

To the best of my knowledge,  two rates  should have matched, but results were: rate realised after revaluation on EURO account was 1.300966; whereas rate found in on CB website for 31/10/2012 was 1.2399443924.