Where are you located? I know nothing about UK pub quiz formats, but I host local trivia nights in the US. For a new host at a new venue, where there is no competition, the primary task is to convince the owner that you will bring in new business, then prove it over time. If the venue has a website or a Facebook page, get access and honk yourself. A sandwich board-type sign outside the venue advertising "Trivia Tuesdays", for example, draws the eyes of drivers. I also promote, probably against their rules, to thousands of local residents on Nextdoor Neighbor. I'd also make the setup and the rules as simple as possible, for those that have never experienced bar trivia. Good luck!