It is possible that, over a generation-scale timescale, there will be some benefits to the UK's position. I don't think that anybody can reasonably argue agains

It is possible that, over a generation-scale timescale, there will be some benefits to the UK's position. I don't think that anybody can reasonably argue against that, simply because of the uncertainty of the distant future. The problem with that: the EU/EFTA is a large economic and regulatory power, with which the majority of UK international trade occurs (60% of imports and 48% of exports). This is basically a consequence of both geographic and cultural proximity. The result is that UK regulatory and trade regimes will be heavily influenced by actions of the EU/EFTA market in terms of regulation and trade policy; the UK will need to remain closely aligned for the foreseeable future. This means that being "outside" that market introduces obvious inefficiencies and costs, with few indications of any economic benefits that may emerge.