The National Council for Voluntary Organisations is an umbrella organisation for many volunatry groups in the UK. It acts as a pressure group representing the needs of these organisations and providing support facilities. Local units exist and if your company has registered it can get various levels of help. The local organisation usually maintains a list of local groups which may be very useful if you require any of their services. Such a list would be ideal for the survey suggested in the question.

As an example I include a diagram showing the activities of the Lancaster District Council for Voluntary Service. (They have a web site). This group certainly have available a list of all local voluntary groups and what they do, and a simialr organisation will usually exist in your area.