a Canadian political campaign (Federal) lasts at most 45 days, with probably an estimated 45-60 days of additional lead up time to prepare for it when it's obvious a vote is going to be called... The parties still seem to find plenty of money to spend on 4/5-star hotels, chartered airplanes, staff, etc.
edit: Regarding this...
> The major parties in all developed countries have permanent election teams with many multi-million pound budgets.
That's very likely. However, the bursty nature of elections means they're probably also onboarding thousands of volunteers and temporary staff in a very short period of time.