Holiday rental ideas

I am looking for ideas to promote a holiday rental in Cornwall (in the UK). Over the summer season it was fully booked, which was great as the website was only made in March/April. Now we are only getting a few enquiries asking for weekend breaks. I thought this is what would happen, but looking at two other places they are fully booked for the next few months.

I know these two other places have been rented out for years and will have repeat custom, something we don't have yet! But obviously the business is out there.

We are getting higher in Google for the keywords needed, but kinda need some more ideas to boost bookings.

Currently done the following:

Built Website, back linking which is slowly working.
Blog on website.
Google places.
Facebook page built.
Listed on several free holiday rental directories.
Listed on one paid local holiday directory.

Will be looking to:

Make some videos, possibly from videohive.
Sort out a newsletter and capture email addresses.
google PPC ( next to no competition)

Online and offline ideas to help things along would be much appreciated.

Im doing this for a family member so not looking to profit out of the work, just help him out and improve my skills.