IMHO, Britannia only lasted as long "in service" as she did because she was a fine example from a bygone era. Fast forward to today, and the amount which would need to be spent to compete with the average Russian oligarch would be beyond our budget, not to mention beyond the capabilities of our shioyards to produce (no criticism intended, but horses for courses...) Factor in the running costs and the inevitable carping over who would use it and for what, and it is all just too hard. I also suspect that the days when "sales" could be closed over canapes and a few tunes from the Band of The Royal Marines are, sadly perhaps, behind us.