Cheap Flights Holidays

i am going to adelaide in november but am trying to get the cheapest flights possible im travelling with my husband and my son who will be 1 come then.. does any1 have any seggestions on how to get the best flight deals as i have been trying the last 3 days and all very expensive..

Travelling from England for about a week or something!!!

My Partner and i want a Holiday in Canada for 4th Aug-24th Aug. Where can i get cheap deals for flights only? Im travelling to ottawa.