Richard
The SIG group of the IIE represents the views of members of the IIE.
The EBME steering group is made up of engineers with a genuine concern for medical engineering.
They are drawn from this forum and are members of various institutes including the IIE, IEE, IHEEM, IPEM etc.
I really don't think that it matters which institute you belong to. It does matter that whoever is on the steering group has the time and committment to push forward the general consensus.
If you are interested in being on the steering group, give me a call on 01279 827533.