The coffee is coming through beautifully and your tip of a "dab'll do you" is spot on 
. It really is too easy to overdo it and make a coffee with a little beer flavour. You just want the threshold of coffee notes from the grain to be nudged up slightly and 250ml in 25l does it. It's down to 1.020 so am hopeful I will get down to the expected FG of 1.014 by early next week, just got to decide on kegging or bottling.