They do run concurrently and the Conservatives are suggesting a change in the law. However, they may face a struggle as the entire principle of concurrent sentencing will have to come under scrutiny.
As well as this there are practical difficulties because, of course, prisoners do not serve all the time to which they are sentenced in custody. They serve at most a half and then are released on licence. There would be difficulties in the defendant not knowing when his ban begins (and hence when it ends); there would also be difficulty in �re-banning� him in the unlikely event that he is recalled to prison.
All in all a non-starter.