The Enquiry received email message is already defaulted to say:
"Thank you for your booking enquiry. We will be in touch shortly. Please note this booking is not yet confirmed"
If you would like to add to this message i.e. ‘Feel free to contact us on XXX if you would like to discuss your enquiry urgently’, you can do this in your Settings:
Select the relevant Booking Type
Scroll down to the Emails section
Enter your message in the ‘Enquiry received email message’ text box
Make sure to SAVE the changes