For anyone that's interested, I ordered the 43.5mm ones from RockAuto - now installed and working fine. 73 USD for the sensors and a few more for the valves - 31 USD the lot delivered by Fedex to the middle east in 48 hrs. That means they cost just over a quarter of what the dealer was asking!!!
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2005 A8L W12 Almond Beige
2008 Jaguar XK Convertible
1971 Jensen Interceptor II (soon to be Mendip Blue)