@Amie9 When you are a traveler making plans for such an important event, having a host cancel is very disruptive for you. It is possible for extenuating circumstances to occur for a host causing the cancellation. Unlike a hotel, most hosts do not have another back up room to offer. However, should a host cancel in order to raise the price of the listing, that is a HUGE no-no on Air BNB and should be reported.
It seems that there are two issues. Most urgently, you need a suitable affordable place. Also, you want to report the financially driven cancellation. I suggest you call Air BNB. The UK number is +44 203 318 1111. Ask for help and make a report. Good luck