You have to remember applying for a mortgage isn’t like applying for a phone contract or credit card. There are a lot more steps involved and given the nature of the legalities and level of detail involved it can take anywhere from days to weeks or even months.
The size of the lender itself impacts things a lot but we can always find out their anticipated service levels.
Obviously it’s within everyone’s best interest to work as quickly as possible to meet deadlines so be sure to note if there are any anticipated dates to aim for.