trifling things=MINUTIAE AI< in MINUTE
Impossible to know=ANYBODYS GUESS as already pointed out ANYBODYS GUES(T)S
connected to paddington(alluding to paddington bear)
=URSINE U (R)SIN(E)
person making arrangements=DISPOSER SID< POSER
If SID seems tenuous as MALE then i apologise. But Mens names are often used in cluing especially the times
The completed anagram does indeed give the answer MEASURED
Well done everyone and thank you for playing
Cheers!