After my extensive reading, the best way to do this is going to be making a cold brew coffee solution (steeping ground coffee in water for 12 hours at a ratio of 5 water to 1 coffee, then straining to create coffee solution) then adding and tasting bit by bit during fermentation/dry hopping period. Reason for this is that IPAs naturally carry a bitterer flavour than stouts and porters because of the hop character, so you don't want to overdo it with the coffee.

Looks like for our volume of beer, 750ml of solution will be enough but we might not need that much using the above method. So, 620ml water to 125g finely ground coffee should be good for the brew.

Have chosen mosaic for its combined characteristics of fruitiness and earthiness, to add that BBNO fruit nose but complement the coffee. Actual lemon addition was not recommended.