I didn't see the television programme but I suspect that the locomotive was A1 Pacific 60163 'Tornado'. Whilst I believe the construction was funded mainly by private donations and much of the work was undertaken by volunteers, no doubt some of that cost will be recouped and most of its running costs will be covered by operating mainline steam charters and/or by hires to heritage railways. I can't envisage an analagous situation for a replica Wellington - all it could hope for would be airshow display fees and museum admission charges. I doubt that these would make it a viable economic proposition. What one hears about the Vulcan would, I think, make any level headed person think and think again before contributing - in terms of finance or labour - to a project that probably would end up as a white elephant. To build and fly a military aircraft you have to be either very rich, very foolish or a government body - and the larger the military aircraft, the larger would have to be the rich person's pocket, the fool's ego or the government body's ulterior purpose!