This morning my 5 year old Sony KV-28DX20U TV started playing up. The
power light goes on, sound comes out but no picture. After a minute or
so, a green tint appears over the screen and then the picture comes in,
but with a green tint.
I believe the Sony's have a self-diagnostic feature, but can't find
much about this.

Its a long shot, but...

http://www.highlandelectrix.fsnet.co...s/SONY.TV.html

Try a combination of searches like "5 flash" and "blink" to find some
possibly relevant codes / module failures