A bit of a late reply but I saw some british podcasters speaking about this issue and the simple solution the british upper crust created to create a social barrier and political or ideological buffer, elocution lessons for the children, they engineered several new affectations of british english in high society essentially creating the posh british accent and setting etiquettes and common verbiage to more easily differentiate outsiders and insiders. Prior to this the british upper class sounded much like the classical high society southern accent from america as it was essentially a marginally changed british high society accent. It might be a bit on the nose but I would say that reviving the high southern dialectic through elocution lessons might be a solution, Let the northerners revive the mid atlantic accent. It truly is a half measure but it might be more feasible than teaching manx.