Thanks folks.

I went away and took another look in the interim, and concluded I'd
missed the array bit (even though I didn't use CTRL SHIFT ENTER on the
MAX calc!!) and ended up with:
{=IF($F$8="",0,SUMPRODUCT(MIN(IF(($D$8:$D$73="H")* ($F$8:$F$73<""),$F$8:$F$73))))}

Works a treat.
Thanks
Neil