Post a link to this website to all your Facebook groups and social media. Encourage everyone around in your local cultural group to meet up together and prepare a submission. Volunteer to help provide historic and current photos and details of your activity.
If you are a member of a nationwide organisation such as the NFU, FUW, CLA, CA, BHSA, BASC, GWCT, NGO etc, persuade them to spread the message via their own memberships to encourage local submissions.
When you make your submission to the Inventory please send a copy of it to your MP. Include photos of yourselves doing your activity, photos of your parents or mentors doing it in the past and photos of young people learning it. Put real faces in front of your MP, with your farm, dogs, horses and so on in the background with you. Provide a brief cover letter explaining why you have applied to be on the Inventory and the requirement of your MP to recognise you as a cultural minority and to ensure your future. If you live in a rural constituency, it will not do any harm to politely remind your MP that the rural votes rely on supporting rural minorities, be it farming, equestrian, field sports, shows and events, small holdings or crafts.
You can find your MP here https://members.parliament.uk/FindYourMP