Mortgage Interest Relief in 2004

I took out a mortgage in 2004 as a first time buyer. I was checking my mortgage statements and I calculated that I got interest relief at 20% for each of the years 2004-2010. Does anyone know if this is the correct rate for my mortgage? I know the rates are 25%, 22.5% and 20% now but am unsure if these were the rates back in 2004.

Thanks.