Nuevo 2007 - interior light cover removal

Can anyone tell me how to get to the bulbs in these high level lights in our 2007 Nuevo please? The covers seem too rigid to just spring out. 

Does nobody know?   

I’m completely guessing here but the cover looks like it simply clips in top and bottom? Maybe the rigidity is because the plastic has deteriorated over time?

I did read somewhere years ago that the do clip in & out, I would be careful as they might crack if too heavy handed.

I would soak a heavy flannel in very hot water, wring it out and apply it to the diffuser at one end to warm it. Then use two thumbs to carefully press the bottom of that part of the diffuser up towards the ceiling, hoping that the bottom edge will lift out of a slight ledge.
That's a pure guess, based on what I can see of your photo. As others have said Take care but warming will probably help.

Maybe also turn the van heating on high for a while?

Just be VERY VERY gentle ! !  

Thanks for the helpful replies everyone.  I haven't had the nerve (or the time) to try it yet but at least I know what I've got to do.

Finally got round to taking the covers off.  Not too difficult in the end, I just hooked something around the end and pulled gently. I hope they go back on as easily. The lights are normal fluorescent lamps, 900mm long on the drivers side and 2x600mm long on the passenger side.  The wiring colours don't match the wiring diagram (the wires are slate/black but the diagram shows slate/orange).  Now I've got to find suitable LED replacements. Any suggestions?