Two weeks ahead is the norm in London. When scheduling your timelines, have two deadline dates. The official date for your start-up project and your internal project/work deadline date.
The official project deadline is the one you will give your clients. It is the official end date used by your business. The other deadline is an internal deadline used as a working deadline to make sure the work project is completed before the official deadline.
The British do not like to be rushed. Trains start at 500 and the weekend starts on Friday at 1500. As a start-up in the UK, plan a conservative deadline timeline and factor in more time. The British have a culture that plans for delays caused by actions, vacations and public holidays. Avoid being a toxic start-up by planning realistic deadlines.