I've been checking the MINI factory tour website regularly for the last few months. In the last week or so, MINI has re-opened their factory tours post-COVID. The 100 minute tour of Plant Oxford costs 21 GBP per adult and must be booked in advance. It looks like tour groups are limited to 15 people or so and run every 2 hours. https://www.mini.co.uk/en_GB/home/why-mini/mini-uk-production/book-a-tour.html