@peekay123 Thanks so much for the reply.
Regarding VBAT you have confirmed my thinking about it use. It has a use but really does not do much for me in my application. I must say your words about the subject were much clearer than mine.
Also thanks regarding WKUP What was bothering me was the Datasheet says you cannot exit VBAT mode via an external interrupt. I kind of view the use of the WKUP pin as an external interrupt (thought I also can see that it may not be considered an external interrupt from ST’s perspective). Anyway for me it seems to be a non-issue as I probably will not make use of VBAT feature.