Hi guys, I got it done. While trying to get them out I spotted that there are two clips on the bulb holder, which when pushed in allow you pull it out with ease.
I tried getting a photo to
help explain where they are, but it didn't come out well enough.
If you twist the bulb holder so the cables run from top to bottom, then look at where the holder meets casing, there are 2 groves on the left and 2 on the right of cables. The tiny piece of plastic between the groves is actually the top of the clip that holds the bulb holder in the casing. Pushing both in at the same time (pushing one in is enough in some cases) and pulling on the holder releases it quite easily. Though I must admit, pushing these clips in is very fiddly. I used jewelry screwdrivers to do it.
Eliminates the risk of breaking the holder in a fit of rage!
Hope this helps someone.