[Ian_A]

Not a happy bunny! Went into the greenhouse to pick some more toms only to notice that some of the plants have blackened leaves...a shame as there are still tons of green fruit that could be ripening. Still I have had some ripe tomatoes this season but not nearly enough for the number of plants I grew. Oh well. Green tomato chutney it may well be....

[arugula]

Are you sure its blight? Some pics to help rule out botrytis and others would be useful. 

[stompy]

Remove the infected leaves and try to keep them going.

Other than that buy a bunch of bannanas place them in a cardboard box then add the picked green toms a few at a time and seal the box with tape.

Check on them daily and they will ripen, leave the bannanas in there and keep adding the green toms as you need them.

The bannanas will ripen the toms quicker as they start to blacken.  

[DD.]

I wouldn't jump to the blight conclusion either. The blight maps show no reported outbreaks in your area and it's even less likely in a greenhouse.

I'd be inclined towards Argyllie's suggestion.