Church House have been in touch to say extensive guidance on how to register your building for Same Sex Marriage can be found on the URC Website under Resource Library / M / Marriage of same-sex couples:-
http://www.urc.org.uk/marriage-of-same-sex-couples.html
The top 3 documents give Guidance and ask people to write to the General Secretariat at Church House if they still have queries.
Update 26.8.16
The collection of guidance now includes some sample letters that could be used in applying for the registration of a local church building, some blank forms for appointing an authorised person, and also a sample wedding service (the inclusion of this being a legal requirement, when a local church applies).
