Preventing double booking of cars in a SharePoint calendar?

I've just finished setting up our booking system. 

Working with 3 lists and power automate.

List 1 is the full inventory with all vehicles and information relating to them. Using a powerflow based on the status in the field 'availability' it autopopulates list 2 available vehicles.  I did originally have 1 list with a filtered view to available but they could still see all vehicles. Once the available vehicle list is populated there is a hyperlink column with custom json to create a button like clickable link labeled "request to book". This opens a booking request form.. This form is the front for list 3. Some slight modifications on the header, body and footer to make it look more like a form and user friendly. I wanted to use the new forms option within SP lists but I couldn't get it to autopopulate the registration on the booking request form. Once I had the lists set up I started working on the flows. 

Flow triggers from the addition of item in the booking list. It then uses a filter query leading to get items to return anything that conflicts with any existing booking using the booking & return date the approval status and the registration if it finds any matching conflicts then it updates booking list to rejected and sends a notification to say there is a conflict and you need to check the booking calendar (this is the booking list in calendar view filtered to show only approved bookings by registration). 

If there's no conflict it then goes through the approval process updates the lists based on either response and sends a notification with various details for the car etc for booking confirmation and rejection. 

I'm pretty sure the flow could be better but I'm still quite new on power automate so any suggestions are welcome. Dean_Gross