Just to confirm what HD says, go-arounds are something that every controller should plan for from each and any approach.
It may be nothing more than keeping a hole available for an aircraft to go - in many cases the crew will get non-standard instructions on the go-around because following the standard missed approach procedure would bring the aircraft into conflict with other traffic. This is no problem for ATC (and hopefully wouldn't be for crews). Granted in the London area this may be difficult to achieve but it's good ATC practice in my book.