Help! Tomato Blight?

[DidoAtTheLido]

I am a very inexperienced at growing anything at all, but very happy that my tomatoes are now ripening up nicely.

However, I noticed that some leaves started to go yellow and spotty, so I have been removing these.
Now one plant has started to look darker - the leaves are going purplish and the stem seems to be getting dark, maybe covered in a fine 'fuzz.

Is this blight?

Should I harvest my tomatoes now, whether green, red of midway, or can I leave the green ones on the plant? Will they be OK to eat?

I get a touch of late blight or similar most years. I just remove the infected leaves but leave the plant in. I’ve had one plant down to about 30% leaves for the last fortnight and still ripening tomatoes. I’ll remove the plant and move the fruit indoors once it stops making progress but it’s still got plenty of green fruit.

I’m terrible at telling what illness is what, so for safety I dispose of all tomato leaves in my kerbside food waste rather than composting.