Hello LeaUK,

You have to pull off the rotary button. On my '90 W124, I needed pliers and a protecting cloth to pull it off. It is fairly common after 12/15 years they feel like stucked in place. Be shure to replace by the right bulb : of the same 2 watt bulbs, my Benz has at least 3 different types. Clear bulb foot, grey or white. If mixed up, you will have almost no light or light where you have never seen it before...!

Danny