A ditch separating the back garden and the house.

doingitanyway

Thanks everyone for comments. 

The ditch runs the length of the cottage only.

I have checked the flood risk and it is very low and low for surface water.

Photos do not show on the link to the property.

You are right to say it might not even be a ditch as that is my (probably inept) way of describing it. 
I have asked the EA to provide further information

Again, thank you for taking the time to post.theoretica said:

How does it compare to the land height at the front of the house?  It is definitely a ditch and not the land being levelled for the house and the back garden higher?

This seems like a possibility as the area is hilly.

Norman_Castle

doingitanyway said:

 I can see the dirt [soil] where the foundation of the house is at the back of the cottage. it is a sort of gulley. I don't understand why. It looks like the foundation has been dug and left.

If its against the wall of the property it may be because the ground level is higher than the damp course. Removing soil from against the wall avoids damp.

Doozergirl

doingitanyway said:

Thanks @Section62 I am probably explaining it poorly and I don't have photos. Not really rural as such and the garden is higgledy-piggedly and on different levels. I can see the dirt where the foundation of the house is at the back of the cottage. it is a sort of gulley. I don't understand why. It looks like the foundation has been dug and left. I don't see any pipework down there...

We have this.  The land is higher at the back than the front. 

There was a point where it genuinely was a case that the foundations had been dug and left.    Now we've landscaped and we have a little retaining wall and a bridge out from our sliding doors.  I love it.  This summer we'll put in a water feature so it's like a mini-moat. 

Think of it as an opportunity to create character! 

doingitanyway

Just to update. I didn't proceed with the purchase as I couldn't get a sensible answer on why the ditch was there.