Thanks for your input, but BS3602 Grade 35 might be an out of dated standard, and I'm pretty sure that it is different with BS3602-1/360. Can you check it out again from your handbook?
I think your material specifiction is based on old standard.
Based on my data FROM LOWER GRADE TO HIGHER GRADE:
BS3601-360(SA/A53GRA,DIN 1626-st.35,STPG370)
BS3602-360(SA/A106GRA, DIN 17175-st.35.8,STPT370)
BS3602-410(SA/A106GRB, DIN 17175-st.45.8,STPT410)
BS3602-460(SA/A106GRC,STPT480)