That is my ceiling. ABCD is something like the following:



I don't see how I can DIY change the main fixture. Last time (10 yrs ago) when my mum ask those people that do the plaster ceiling they went for G24 (PLC 2-pin) for reason that I don't know what, probably that time still easy to find such bulb. And yes I think this is called downlight like you say. If I can DIY most thing for sure I'll change to E27 base but I'm out of idea now. Probably if ask electrician to come change also they might need to break the plaster ceiling.

I see..I've seen that philips light in shops before. I'll try again see if I can take out the current fixture (I did tried in the past few years back, pusing2/tarik2 but fail). Hopefully it can be done and the wiring is not hard to do. TQ.