I bought this a few weeks ago and have put off using it due to extreme
vagueness/info on measurements when using bread mixes, long story
short.

Anyway, I decided to just try my standard measurements I use with the
Breville. No problem there, it's all set to go and I pressed 'start',
it's been sitting in 'rest' mode for the past 15 minutes (and
counting).

This last bit has me puzzled... why on earth would it need to 'rest'
right at the start - the bread mix, yeast and water haven't even been
mixed together yet.

I'm no expert by any means when it comes to baking, but can anyone
explain why it should rest at the start like this?

NB: The machine is definitely set correctly according to the manual.