is there anywhere which sets out whatever consensus there is as to what constitutes a "tikka masala", a rogan josh, a bhuna, a balti et al?
I'm sure there is, and Wikipaedia would be my first thought (I haven't tried it), but from my perspective (let's see if there is consensus) :
A (chicken) tikka masala is the BIR take on the classic chicken makhani, comprising pieces of chicken tikka in a mildly spiced creamy tomatoey buttery sauce, often with ground almond or similar being added.
A rogan josh is a classic dish adopted to BIR taste; normally made with lamb, goat or mutton rather than chicken, it comprises meat in a red (from the Kashmiri chillies used) medium-hot sauce containing a little yoghurt; the modern BIR version tends to add onion and tomato.
A bhuna is again a classic dish which uses little or no base, the whole essence of the dish being that the meat, onion, etc., juices provided the necessary moisture; it is a mild dish (but not as mild as a korma) in which the meat, onions, tomato and spices are gently cooked in oil until nearly ready, then "bhooned" (cooked at an elevated temperature) to accentuate the flavours and bring the dish to its final state.
A Balti I have never eaten; it is, in theory, cooked and served in a balti dish, but in practice it is often cooked in a conventional pan and then decanted into a hot balti dish for serving.
** Phil.