I'm inclined to agree with your HPT assessment... If you've got a BT booked there's no point really - it just adds stress. Either your BT will be positive, or AF will come - would getting a colourful stick a few days early really change that much for you???
(This last cycle was the first one I managed to hold out and NOT test, and waited for the BT - so when I got the positive it was with a number that meant something, not just a vague 'how dark is the line' guess sort of thing!)