How quick should paracetamol/calpol work?

My 1 year old has a temp of between 38c (100.4f) and 38.5c (101.3f)

Its currently 7am here and I gave her calpol at half 6, checked her temp again and it hasnt come down below 38c....

Shes very snotty and clingy which obviously isnt like her- doctors dont open for another hour but I wondered how long it should take for the medication to bring her temp down?