Bulbs are identified by a short number (it’s even printed on the bulb’s base) and can range in price from less than $15 to over $200 (for HID, or High Intensity Discharge, units).

However, LED and HID bulbs are far more expensive to buy than halogens, and some car companies have also switched to sealed headlight units that can’t be opened up in order to change a blown bulb.

To replace a traditional halogen bulb on a Volkswagen Polo costs owners just £18. However, buyers who choose the high-spec GTI model face a £846 repair bill for the car’s LED sealed headlight ...