Further update - was looking at the thread K770/K770i Flashing red light / Dead :( €10 for you to buy a few beers?? who had the identical problem. So I tried KKClient and the eron update worked -

Press "5" and "2" keys, hold them together and plug DCU60 USB cable.
Phone Connected...
Detected: DB2020: A1 Series
Flash ID: 0x897E - Supported
EROM CID Detected: 51
Status:3
EROM Update Ok!
All Done! - Time:00:00:00


However, the phone will still not turn on and I still get the one led flash so by all accounts nothing has changed! Help!