Trimmed mean for grouped data

I've never used TRIMMEAN but as I understand it....assuming post code are in column D and times are in column F and the target post code is in J1 try this array formula.

Formula:

=TRIMMEAN(IF($D$2:$D$4=$J$1,$F$2:$F$4),0.5)

Array formulas are not committed in the regular way. You commit by pressing and holding Ctrl + Shift as you hit Enter. You will know that it has been entered successfully when you can see curly braces {} around your formula in the formula bar. You do not type these in yourself. Excel does it for you.

Does this give expected results?