I met with Kate Bellingham of School Gate SET last week. She is looking for volunteers who can help out with STEM activities in primary schools, particularly in the Hertfordshire area.
See http://schoolgateset.blogspot.co.uk/p/about.html?view=magazine for more information. There are also some great ideas on this site for STEM activities for young children.
If anyone is interested in getting involved, please email Kate at schoolgateset@gmail.com.