If the bulb fits in the base, it is the right kind. It could be a problem with the fixture, but it could be anything else along the line as well, a bad switch, bad connection somewhere, faulty insulation, chewed by rodents, etc. RCDs are very sensitive, it doesn't take much current leakage somewhere to set them off.
If a careful visual inspection doesn't reveal anything, about all you can do is take various components out of the system until you find the one that was tripping the RCD. For instance, test the fixture by removing the wiring and connecting the wires to a simple keyless base with a light bulb installed. If the RCD does not trip and the bulb illuminates, then you know the fixture is at fault.
If the RCD still trips, then the fixture is not at fault. Next try taking the switch out of the system by wiring the switch wires together so that you have an unswitched circuit. Test again. If the RCD still trips, identify intervening junctions and connect your test light at each one, starting at the switch and working back towards the distribution panel. You will eventually make a connection that does not trip the RCD. Then you know the bad section is immediately upstream from the successful connection.
I've left out many safety details here in order to outline basic trouble shooting. If you are at all uncomfortable working on building electrics, do not do any of this, find someone that knows what they are doing. Also, if you have an older UK ring system, these confuse most people, you need to find someone familiar with this rather unusual arrangement.
Usually it is the lightbulb itself. It can be that it is nearing its end of life and simly needs to be replaced, or it can be that it just isn't fitted properly. The next best thing but quite unlikely with devices like this, is the powerswitch.
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Just looking the fixture itself, and giving the probability of other points of failure... I would guess maybe the ballast on the lamp has given out (probably the silver box in the image). A ballast steps up the voltage so the lamp operate correctly, and they fail on occasion. Finding the replacement ballast might be the hard part and sometimes expensive. It might be easier to just get a new fixture and use CFLs (which have built-in ballasts).
At the same time purchasing a new fixture and replacing it will also confirm, in a relatively easy way, that the wiring to your fixture is working. Just be sure to throw the breaker to that fixture. Don't depend on someone wiring the light switch correctly and given your uncertainty of the status of your home wiring.