Left it charging overnight and batt appears charged as led has gone off.
Power led is permanantley lit but nothing.
Take out battery power led off press power button led lights battery led flashes but nothing.
Power led remains lit until battery removal.
You might want to take a look at your RAM. Odd thing about laptops (based on my experience with some repair work I did on both a Sony Vaio and a few Dell Inspirons) is that if the RAM is not properly seated, or just simply bad, the laptop doesn't power on. No POST, no video, no nothing. Reseat the RAM or replace them, and voila. Power.
Exact same situation here too with a PCG-7185m, of similar age (16/17months).
Stanna, have you made any progress with diagnosing your issue? Have tried a new battery, reseated the memory, and removed hdd and cdrom drive (in case either component may have been causing a short somewhere).