Naive, not really - just informed. Given that the De Havilland Vampire was a subsonic aircraft and originally designed for service in World War 2 which had ended before it eventually went into mass production I don't think I'm at all wrong by saying that it was obsolete as a fighter aircraft in 1956. In fact if you read old issues of the Irish times etc from the mid 1950's even they criticize the Department of Defence at the time for selecting an obsolete fighter design.
By 1956 far more technologically advanced fighter aircraft had superseded the 1940's vintage Vampire such as the North American F-86 Sabre and F-100 Super Sabre which had been already introduced to service in both the USA and other NATO member states, the Hawker Hunter in the UK with the English Electric Lightning to be coming online a couple of years later, the Mig-19 in the USSR, along with the Dassault Mystere series in France and the soon to be online super mystere etc etc.
RAF Fighter aircraft from the 1940's and 1950's that were found no longer deemed suitable for day time fighter operations(because their performance had since been superseded by enemy designs) usually ended up as night fighters where manouverability and performance was not as major an issue hence large numbers of Vampires in RAF service ended up as ''night-fighters'' as well being used as ground attack aircraft(in lower intensity conflict areas where the threat of much more capable enemy fighters wasn't really a factor).
As far as the RAF using the Vampire T11 trainers the arrangement did not last all that long as they were replaced in the early 1960's by the supersonic Folland Gnat.
Any way one looks at it it simply cannot be justified that the De Havilland Vampire T55 was a state of the art fighter aircraft in 1956 I'm sorry to say!
And having talked to two former Air Corps Pilots who actually flew them in the 1960's they were largely hangar queens compared to the rest of the fleet at the time due to the expense of the engine replacement, maintenance and cost of operation. One of the two had to complete his Wings course on the Piston Provost after only flying about 10 hours on the Vampire as all the Vampires then went for maintenance and it turned out that they didn't have the budget to get them up and running for the forseeable future at the time....