What do you expect a Chicken Tikka Masala to taste like?

I’ve ordered Chicken Tikka Masala from numerous takeaways and restaurants, tried different ready made meals from supermarkets, and have used different brands of sauces to cook with. The thing is, they all look and taste different to me. Some have coconut in, others don’t. Some are quite tomatoey and tangy, others are more like a red coloured korma and are very sweet. The variation is so much that they could all be a different dish themselves. Is there a standardised, or at least a regional, recipe for Tikka Masala? What’s your take on the popular British dish?