What about ISA and General account? Do the same shares of the same company need to be pooled too?
Yes, it is a pain, especially now, when it seems there is more and more brokers coming with interesting propositions. I think the biggest issue is to have the same stock on different platform denominated in different currency. In such case the gain might turn to loss or loss to gain. Also it is a nightmare to access if the stock is gaining or loosing if you thinking about sale and it is denominated in different currencies in different accounts. FX fluctuations can make all the difference.