The OpenStreetMap Foundation have taken the decision not to hold an international "State of the Map" conference (their Wikimania) this year:
https://blog.openstreetmap.org/2015/02/25/openstreetmap-events-in-2015/
There will, though be a "State of the Map" in New York on 6-8 June:
and "SotM-Scotland" in October:
http://wiki.openstreetmap.org/wiki/State_of_the_Map_Scotland_2015
I wonder whether WMUK have thought about offering support for the later, and making expenses available to allow chapter members to attend, in order to foster greater inter-project collaboration?