Im back again like the proverbial bad penny

so I have a couple of questions this time ...
First the easy one ... the bongo is in need of a new starter battery and a new leisure battery ... any recommendations would be appreciated.
Secondly ... this is a bit of an oddity but hopefully someone can point me in the right direction. Every now and then, once the engine is at temperature , it has a little hiccup. I dont think its a misfire but the revs drop and then come back to normal. Also if the foot brake is pumped the revs drop and the engine stalls. I have also noticed the idle revs are a little lower than they used to be. All of which I was told suggests a vacuum issue and I have had a look around the engine and traced the vacuum hoses but there are no obvious issues. So before I take the bongo to the garage I was wondering if anyone here has any suggestions.
Many thanks in advance
Pete