Great Britain Philatelic Society

I am looking for what should be two easily obtainable stamps, but they are proving to be somewhat elusive.
I require to purchase good used copies of GB 1858 Two Pence Blue Type G2 SG45 Plate 8 'RE' and Plate 12 'IH'.
These two stamps are needed to complete the variants of Plates 7 through 15 in used condition.
Thank you.