As a post script to my post above it occurred to me that I might be able to answer my own question by comparing the cards for the ECC84 with those for the PCC84. After all these valve types, with the exception of the heater rating, are identical.
So, I looked up the cards for the PCC84,
OH DEAR, there are 3 of those as well - namely 655ABC. There are differences between the 655 cards and the 713 cards of course because of the differences between the heaters but my comments on cards 713B and 713C apply equally to cards 655B and 655C.
There are also 3 cards for the UCC84