The opinion of a qualified MR Search Manager: In the UK, W3W is pointless! It is a proprietary grid system, which uses words instead of numbers. If you are a UK user, please, just download a simple app that will give you an OS grid reference. The open source OS grid is more logical if you need the emergency services to find you. If you get an OS grid wrong you can still be found fairly easily. Get a W3W wrong and you could be waiting much longer.