Letter for Visa

Hello,

Please can I get some help in regards to a format for a sponsor/cover letter on a tourist visa application?

I am a British Citizen, in full-time professional employment. My parents would like to visit me for 2-3 weeks in the UK.
They have access to their own funds, but I would like to supply a cover letter regarding my relationship and evidence of my funds and where they can stay too.

Could someone share a format or a sample letter as a reference, so I work out how to draft one covering all point applicable for a family tourist visa [i.e. for my parents to come visit me] please?

Thanks in advance for your advise and replies.

What you wrote that is to be in the letter is already a draft, it's for you to flesh it out. There is no format provided on the forum, you can try search Google or other search engines.
After writing you may come to ask here for opinions if it's alright.