Changing land covenant??? UK law?

You dont need planning permission to build a wall that does not exceed 2 metres unless it as a highway. If you think they have breached this, you should report them to the Council's planning department immediately. Unless they receive a complaint from someone (ie you) they wont act and wont turn down a retrospective application. Checkout your council's website to find their email address and send them an email. You should also tell your council's planning department if this shop is breaching the covenants on its land. Not the complete answer I know, but it's a start.