My club wrote to CAA seeking extensions beyond calendar life + 20% for two O200's. Result entirely predictable. No.
GR24 makes provision (or at least implies that it does) for extension beyond calendar+20% with written permission of CAA. Authority's reply to us clarifies this option - only to be used 'to provide for operators who are experiencing an unforseen circumstance and require a small variation to the 20%'. They quantify 'small' as a month or so. Also tried to point out difference between wording of Teledyne Service leaflet, and GR24 in terms of life or hours 'whichever comes first'. GR24 uses the latter for all applications, the SIL uses it only in relation to engines used for crop-spraying. No joy.
Pity that harmonisation of engineering (GR24) hasn't been matched by operations harmonisation - doesn't continental europe class club operations as 'private'? Ho hum.