The CAA do not issue SE(JET) type ratings;one is issued an `Aircraft type rating Exemption,under Article 242 of the ANO 2009,for ex-mil jet aircraft,either single or multi-engined.
It is not necessary to take ATPL exams before flying/displaying high performance aircraft.
In the case of ex-mil jet aircraft,one has to do a conversion course on the particular aircraft,both technical and flying,in accordance with CAP 632,depending on previous experience,before being issued with a full exemption,subject to satisfactory standard of technical knowledge and handling skills.