I'm a Londoner living in NZ and have recently started by BIR cooking journey. All the reading I have done in books and online say that each restaurant cooking BIR food use a single base gravy. Here in NZ I have found two different Indian restaurants that use 3 different bases out which serve as the base for all their dishes. And I don't mean three variations of a similar base - but three actually different base gravies. Then the other day I asked my local Indian TA and they confirmed they have 3-4 bases. Of course I asked for a hint of their recipes, and while they declined to give them they did say these different base sauces are online. But I haven't found them yet. With that in mind, I have two questions I'd love answers to:

1) Do British BIR TAs (as opposed to antipodean BIR TAs) use multiple base gravies?

2) Does anyone know where to look to find multiple Base Gravy recipes, with accompanying curry recipes?

Thanks,

Elimilech