I made this today for the first time. I did take a previous poster's advice and replaced the Pataks tandoori paste with the tikka paste, but otherwise it was exactly to spec.
Lemon juice was 4 tablespoons freshly squeezed.
It was very nice and my 5 year old son really enjoyed eating it too.
I will probably adopt this for a while as the great thing for me is not having to buy a pint of yoghurt that gets thrown in the bin a few days later.
Cheers,
Paul