Sir: Mr Smith argues (correctly) that we currently need higher interest rates in the Southeast and lower rates in the rest of the UK. He (correctly) argues that such conflicts of purpose will increase if we enter Euroland. He then (incorrectly) goes on to suggest that this is an argument for staying out of Euroland.
In fact, he has merely highlighted a major deficiency in the use of base interest rates as an instrument of economic policy. He has highlighted the fact that control over UK interest rates is not worth hanging on to, because it cannot even cope with what is just a UK problem.