The UK application center in London instruct I need letters of invite to get visa

The destination I wish to go is in Yangshou only the organization there do not supply invites plus which way do I go to get to Guilin airport from Uk I'm confused as I thought to get to Guilin airport from arriving at Hong Kong I'm still confused about visas and Hong Kong and the best way to Guilin by plane from England also what type needed? Can you help me mmake sense?