Please can you advise if it's possible to put more than one set of codes onto a GW card, i.e. such as SECA & A.n.other ? or is it best just to stick to one set & this will also save constant swapping of cards from cams etc.
It's not a question of keys, it's a question of whether there is a means of putting the decryption algorithsms/etc (ie the actual software) for more than one system onto one single goldcard.
The answer is yes, but such cards can only be used in combination with a limited number of receivers/CAMs since they have to be patched as well (any given CAM - embedded, CA or CI - normally allows the signals from just one single encryption system to be propogated to the card).
A working example is the "irseto" goldwafer fileset for use in a suitably patched Irdeto CI CAM. This gives Irdeto as well as Seca - though the memory restrictions of the chipset on a standard goldwafer mean that the number of actual keys that can be stored from those systems on the eeprom is limited).
Read all about this and other multi-encryption options elsewhere on this board (search for 3-in-1 & DS9 & FreeCAM2 for starters).