Mains power cut to house - iMac now DEAD

Today I turned off the mains power to change a light bulb in a room that has given me some problems with sparking in the past. Unbeknown to me, my son was using my iMac... (no, I failed to check properly, now I am suffering, believe me😢..). After I switched the power on, my son exclaimed "Well, now the computer won't turn on!" We have a surge protector which would have been on and working, but as the computer - a 17" intel duo core iMac purchased new in mid 2006 is old, and the surge protector is the same age, I am sick with worry wondering what it could be, and there are no repair shops near us open tomorrow, or even in our town! I have to wait a week, and travel 100kms to the apple service specialists.... This computer is home to all our music (massive amounts my son has on there) and my photos - thousands, a serious hobby. As well the computer runs Final Cut Pro Studio software, as we do a bit of video editing. I have backed up no files, always meant to get around to it..... As the computer is older, the main thing that devastates me at this point is my photos - a life history really, and thousands of hours too, photoshopping, etc..... I have tried to computer in different power outlets, tried turning on, off, unplugging, all I can find recommended on these kind of sites - but to no avail. The screen is black, and not a sound can be heard. Completely dead. Not one sign of life in the 8 hours since..... I have been reading about PRAM batteries... this computer has had a massive amount of use, daily and in the house of serious creative insomniacs - for six years now, so almost daily serious use, and as yet just two dead keyboards, no other problems.... I got some extra RAM when it was purchased. But recently it has not liked shutting down (it hasn't) so it has been pretty much permanently on, with the screensaver up,..... could this suggest a dying PRAM battery? experts please, this internet reading has done my head in, now I have to wait a week!!!!! to know if our photos and music can be recovered.... if not the computer itself revived....?

Thank you for any help. I know, I am SUCH an idiot for not checking all electronic devices were off, but as we know, this MAC hasn't been turning off recently...