as i understand it. the law(uk) still needs a court order. as they would to tap your phone! could be wrong?
as i said you could use a PGP prog(there is a lot of them) as all sides has a key.however they(law) can ask you for the key!fact.
never had to use any PGP prog. just know about them.
however where all this falls on it a##, is when one of you, keeps a backup for REF.
so in my opinion this is not the way to go!