Extending the mains water pipe into the garden

[Mrs Money Pit]

Hi there, first post so please be gentle with me!

Not sure if this is plumbing or garden but put it here as seemed to fit better.

I currently have a mains fed outdoor tap positioned just outside my conservatory. It exits the wall on 15mm copper pipe, with an elbow and standard garden tap. For practical reasons I want to relocate this water supply to further down my garden, mostly a straight run but about 15 metres along the wall.
What's the best way of doing this?
i.e. do I have to use MDPE or can I use something like barrier pipe? (bearing in mind I am joining it to 15mm copper pipe and will want a tap at the other end).
I intend to bury the pipe about 12 inches below the surface for all but about 1 metre of it. Will that provide enough insulation to prevent freezing or will I need to also lag it along the whole length somehow?

Thanks in advance for any advice you can give.

 

[PrenticeBoyofDerry]

The pipe is best either being one of a non-corrosive material or if metallic it would require protection against corrosion.
It is wise to consider ground movement, so the pipe does not become stressed or fractured by this.
The depth of buried pipe for the prevention of frost is 750mm-1350mm. If these cannot be achieved then the pipe most be thermally lagged in a moisture resistant thermal barrier.
I would also locate the pipe in at trench at least 400mm if the 750mm cannot be achieved, this would help prevent the pipe from being mechanically damaged by garden tools.
You would also protect potable water against any possible contamination and a double check valve would be recommended, this should be fitted internal to this pipe before it leaves the property.