Please understand I'm not advocating referendums for any of these issues, I'm just trying to show how allowing one referendum might be the thin edge of a wedge that could lead to referendums happening all the time. We would be on the road to a type of participatory rather than representative democracy.
Actually, I do think we ought to have a referendum on the reform of the House of Lords.
Boundary changes for constituencies are trivial and happen quite regularly based on the population size of any given constituency. The Boundaries Commission is simply an impartial body there to prevent the rise of ‘rotten boroughs’ like Old Sarum happening again, and constituency changes do not happen for political reasons. Holding a referendum every time there is a population shift would be ridiculous...