Hi Chris
I've used gram flour before, there's not that much difference.
The restaurants were on the Wirral in Merseyside. They might've used gram flour but I never saw it. I know that every corner is cut to shave off costs so I reckon the BIRs I went into probably wouldn't use gram flour in a bhaji when you can get a good result with the plain flour you use in naans etc.
Try them out, they taste the part and cost pennies.
I fry them off in my bhaji / samosa fryer, the oil hasn't been changed for an age, this may change the taste.
I think some of the recipes here seem to be overcomplicated for what is, after all, a very simple starter.