The trick to avoiding that is that your blended concentrates will be things like (Blended) strawberry, or caramel, or in this case cream base. So you wouldn't add your strawberry base into a mix with strawberry in it etc.
The recipe in the OP is a blindingly good cream base btw. I found it somewhere on the Internet and have recently been experimenting with it. It is like the best clotted cream you ever tasted and all you need do after that is add in whatever you want to the blank and cream. Seriously good.
The CAP V Custard is V1, yes?