It is my intention to install a shower and bury the hot and cold pipes
in the wall, which will be tiled over. Any tips, such as copper or
plastic, don't do it, or anything please?

Do it. Get a flush mounted mixer if the wall is deep enough to take it. They
look fantastic with no plumbing visible.

Both copper and plastic will be fine. However, some mixers would prefer
copper as they are secured by their pipework rather than being mounted
themselves. This especially applies to bar style mixers.

Christian.