I'd make its first mission really to replace Amazon with the Royal Mail, which would become BritCo's mail service.
Building a web-site to be a store-front for every UK-retailer, with warehousing and processing done by British workers. Building BritCo for the future of the nation wouldn't even be that hard. Amazon is just a compute infrastructure and software. We need British versions of those things anyway. After that it's just warehouse space.
Alongside that you can clean the rivers and build green energy and generally a supply-chain that is owned by the workers and not by multinational private capital.
This path is probably not compatible with a rejoin-EU I'm afraid.
Not without reforming the EU first, and sadly that is also an institution basically owned by multinational private capital and in which you can get any policy you like so long as it enriches private multinational capital.
