apart from the fact that your not meant to do it unless your a corgi registered engineer there are specific requirements to be met involving the depth the pipe is required to be buried below different materials i.e. slabs, concrete, tarmac etc and also the pipe needs to be laid on a sand bed and either wrapped in a suitable material to prevent corrosion or better still plastic coated copper should be used.
i don't know all the regulations off the top of my head, they are contained in the appropriate british std for pipework which i do not have a copy of at the moment.
pipework run around the outside of the house above ground level does not need any protection. i know it looks ugly, perhaps you could paint it to blend in with the brickwork or put it in trunking of some sort?