FPP144 worked for me. 148f and 147FPP didn't work for me.
I found before Christmas that the codes seem to half the price of the P&P down to 1.75 if you are ordering 1 book... but if you order 2 or more then P&P is completly free
Don't work. It says the code is accepted but the P&P is still on the final order.
Aaaaand, yes, none of these work either.
And 149F should hopefully work as well... :) I'll add all these to the OP for future reference.