The LEDs came from a 24 lamp unit bought in a £-shop for peanuts (the only way to buy them).
The lower component is a diode to protect against polarity errors, and the LEDs are two paralleled layers of three in series. They were mounted on the bayonet from the faulty bulb, so can be replaced to original spec.
Main problem was getting the light assembly apart in the first place!
I'll probably be less reluctant to use it now that it's more frugal with my precious amps.