One of the problems with Labour's English regional plans was that the boundaries of the regions had been set by the central government. The people who lived in them have never been asked if they wanted to be in that region.

Maybe the Spanish procedure could be borrowed... From the Spanish Constitution of 1978:

Section 143

1. In the exercise of the right to self-government recognized in section 2 of the Constitution, bordering provinces with common historic, cultural and economic characteristics, insular territories and provinces with a historic regional status may accede to self-government and form Self-governing Communities (Comunidades Autónomas) in conformity with the provisions contained in this Part and in the respective Statutes.
   
2. The right to initiate the process towards self-government lies with all the Provincial Councils concerned or with the corresponding inter-island body and with two thirds of the municipalities whose population represents at least the majority of the electorate of each province or island. These requirements must be met within six months from the initial agreement reached to this aim by any of the local Corporations concerned.
   
3. If this initiative is not successful, it may be repeated only after five years have elapsed.

Replace province with county, obviously. The Greater London Authority, Scottich Parliament, Welsh Assembly and Northern Ireland Assembly could be grandfathered in without having to go through the process again, but they could reform their statutes.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman