Fixed!!! ... (see edit)
I started from 100% scratch. I use an old laptop with winxp to do all my phone work. I did a factory reset on it (begrudgingly) and reinstalled everything*. ADB, flashtool, drivers/kernels etc. (Its now working a lot better I have noticed).
Bear in mind my phones state was factory stock ics 4.1.B.0.587 and locked.
I unlocked the phones bootloader in flastool, it turned on?! Resurrected.
I flashed the ics rage kernel and installed a custom rom, backed up x2 ;0) I AM HAPPY :0D
I honestly tried everything methodically beforehand, hence my post!
*Is it possible to install a corrupt zip? I noticed when downloading files that some were showing as downloaded but were not the correct file size. I only noticed this when grabbing a kernel file, its size was around 6.7mb but the file I had on my desktop was 633kb, it unpacked and came up with the correct size of 6.7mb? (downloaded on my main work laptop with windows 8.1). I had so many bits and pieces on my xp laptop, swapping files from usb pens etc I will assume this could have been my issue!
lol... I must have spent near to 6+ hours reading about tespoint method flashing, TA restoring/backup up, and a whole range of other bricked device issues... I am educated a little bit more now, in more ways
The phone worked for about 30 minutes and then a blank screen again. No CWM, because of blank screen. Had fastboot and flashmode still.
So from scratch again, I relocked and flashed with original ftf CE (I have two CE ftf's of different sizes (will need to do homework on these)). The phone was still dead? When plugged into my pc (tried all three USB ports), sometimes when in fastboot/flashmode the device keeps connecting/disconnecting randomly, which is definitely wrong. Possibly my problem is a bad port or maybe the micro usb cable, or loose connection somewhere? Irdk? So now I tried a brand new sony, original, cable and all seems fine again. So, used flashtool to unlock, flash kernel, get to CWM, use my backup and the phone is working again.... but for how long? There's definitely an issue with the ftf files (mabye something to do with my corrupt file size problem? Will go to another place to grab these from and if the phone goes off again will try). odd.
The phone is now running okay. I had a dud battery, which I was using/swapping between several phones that I was returning to stock. It was showing 100% charged but upon disconnecting USB the phone died. Took me the best part of two days to figure that one out... I know! (I'm very busy). So it was possibly the bad battery all along!