Thanks leolaohoo. Lots of considerations, many more than I anticipated. To be honest, I think I'll leave all this to the wireless survey as I don't want to waste members time when a wireless engineer will work out all this detail for us.
Thanks also fbarboza - I didn't realise that. I will look into it a bit more.
I also found out, after my initial post, that all the 1262 antennas are external, so it will have 6 in total if we want to cover both frequencies using 'rubber duck' dipole type. Therefore, the physical connectivity of the 1262 is making more sense now and please ignore the part codes in my initial post.