1) Can bare copper pipe be buried (viz. with cement & plaster rendering
afterwards) in a brick partition wall ? If not, what protection measures
should be taken/are available ?

There's something called something like Dobbo tape which I *think*
British Gas has tested and cleared for use when burying pipes. I think
you wrap it around the pipe. It's basically a fabric tape, around 5in
wide, which is coated in a weird kind of grease. It's water resistant
and very messy to use.

Not sure if it's called Dobbo. Something like that. It's cheap stuff and
sometimes recommended for fixing leaks in water pipes as a temporary
solution.