It is not necessary to have anything more than a PPL,apart from a `Type Rating Exemption` from the CAA,and after suitable training.If it is multi-engined,then one needs a ME rating.All `warbirds` are generally classed as `Annex 2`,they do not have a specific type rating,and usually operate on a `Permit to Fly`,irrespective of whether they are fixed or fling-wing,piston,or jet...