Karen Inkster of Ramblers is leading the campaign to resolve this issue, with support from the LDWA and others. The problem is primarily within the ambulance control rooms, where equipment, software and staff training standards vary from one ambulance trust to another. For more details go to http://www.ramblers.org.uk/Campaigns+Policy/999_campaign.htm
I will be attending a meeting of the Inland Consultative Committee of UK Search & Rescue on behalf of the LDWA in June. UKSAR are working with Karen on this through their channels, and I will report back on developments. You can add to the pressure on the department of Health to prioritise this issue by completing the email on the Ramblers campaign page.

There has been recent comment in the Strider of emergency services not recognising grid refs but requiring the relevant post code.

It is possible to convert a grid ref to a relevant post code and vic versa using the web site" street map.co.uk"

However remember that though grid refs define precisely any location in the UK, the limitation of Post Codes is that they are intended to facilitate the delivery of mail and relate to addresses of buildings within an area of ground of variable size. In a built up area this is quite mall but in the countryside this may be of a considerable size. Try resting the system using your own address,

You can also use your post code in Google maps to locate a place on the map or view the satellite imagery.

In a real life emergency anybody with a suitably enables mobile phone(and a signal!) could log on to the site and do the conversion before dialling 999.