You are not going to believe this! Tried everything listed with the config.txt file and still no joy. Decided to look into the startup light procedure in more depth. Removed the RS Components branded cover and bingo! Working straight away!

Many thanks but I'd actually already found that before posting. That response seems to address 'no hdmi output at all' but my issue is specific to one TV. Works fine on the Bravia, same Pi, same lead, produces no picture on the Panasonic?

My Pi boots and displays OK through HDMI to my old (five years old) Sony Bravia but when connected to my new Panasonic E6, there's no video display. Even using exactly the same leads? Can anybody offer a clue as to where the problem might be?