I posted the link to the recipe for Balti Cicken (from fresh ingredients, ie: not base gravy) further up the page. Yes, it is the Balti Brothers (Rishton) and that video is almost identical to the linked recipe of Chef Zaf Hussain's recipe (ie: Shababs). From memory the difference is Shababs uses Cumin, Rishton doesn't.
Here it is again:
https://curryculture.co.uk/balti-recipe/The reason I suggested George cook this first Santa, is because it will be quick, easy and cheap to produce one single dish. From this George could then provide an answer to many questions. I've tried all of them, MDB's, Misty Ricardo's version of Shababs and the from scratch (Shababs / Rishton).
If the single dish from scratch is similar to, or the same as, the Shababs Baltis George has tried, then we know that's it. This would also confirm that it isn't anything like MDBs base gravy dish (a 100% clone from a different restaurant). I can tell you already, they aren't the same. The 2 Shababs methods are similar to each other but the base gravy method is very strongly spiced. My family found it too spicy. I liked it.
If George says that the Baltis he tried at Shababs were less flavoured I'd then suggest he tries MDB's base. If he thinks they were more spiced then I'd suggest he tries Misty Ricardo's Shababs Balti base gravy.
Easiest things first, process of elimination, basic problem solving.