My observations on approach to a junction are something along the lines of: start identifiying hazards as soon as possible, look specifically for any potentially hidden hazards – i.e. bikes, kids, cars moving off without indicating, then look for gaps in traffic, then recheck for any changes to the hidden hazards, check to the sides and behind, check that gap is safe, then move off – then finish up looking to see if you have to take evasive action due to missing something……
Takes a few seconds at most.
No quick glances involved. Position in seat is changed if there is a risk that something might be hidden by pillars.