Hi @Niall-and-Carlee0
No decent marketing person would be on sites like Fiver which pay peanuts.
It would be madness to handover your log in details to a stranger you no nothing about.
It's easy enough for you to sync calendars using one of the STR management software.
You can ask a local established superhost in Bournemouth with five star reviews to review your listing for a fee and advise on matters such as photography, content etc. Or you can post your listing here and ask for feedback.
Personally I found your description of your studio accommodation rather confusing. You call it a studio, yet your photographs with the bed are labelled as a bedroom. Which is it? A one bedroom flat or a studio.
If a studio I wouldn't market it for four people.