Since UN sanctions are certain to be imposed sooner or later , I suggest some prudent enquiries may be in order:

• Examine the names of all Iranian firms your customers regularly deal with to ascertain those you find which are linked to the defence and high-technology industries, and thus prime candidates for sanctions should they be assisting in the WMD or missile programmes.  Have you run the names of your clients' Iranian customers through World-Check ? 
• Check to see whether your bank has a correspondent relationship with any banks located outside of Iran that are wholly owned by Iranian banks, especially those in the UK. Is there any nesting occurring involving Iranian entities already on the sanctions list operating through those wholly-owned banks and into yours ? Have you even considered the possibility that this is going on ? what about Iranian banks operating in Dubai, are you doing business with them ?
• What about those few major Iranian banks not on sanctions lists; are you dealing with them, and if so, do you have an action plan prepared, in the event they are sanctioned tomorrow ?

The idea is to minimise the stress and delay when Iranian entities and individuals make the sanctions list, to seamlessly terminate sanctioned customers, or customers' customers, and to anticipate the parties involved, so that your staff will get an early indication of who may be next.