are they in a greenhouse or outdoors Lighty?, outdoors could be put down to the weather but not sure if GH?
take a few of the biggest off and put in fruit bowl with ripe bananas ( or a paper bag)

thanks - they are outside and have done really well - looking great but the wrong colour! Loath to take them off in case they also go soft as well as red!!

I gave up growing tall tomatoes. I now only grow bushy cherry tomatoes outside and they are all guaranteed to ripen.

They need warm sunshine and plenty of it to ripen up - in a normal year, we would have got a fair bit of that this month and last. Its keep your fingers crossed and hope the weather bucks up, or you'll be making green tomato chutney...

Green tomato chutney is a great favourite in our house and last year I deliberately picked early because I thought there would not be enough left after they'd ripened. This year, of course, like most people with large outdoor tomatoes, I may run out of jars to put the chutney in! However, an edible alternative is to fry them (bad for the waist line but wonderful).
http://simplyrecipes.com/recipes/fried_green_tomatoes/ has a good recipe but there are others.

I agree with costas I grow cordons and bush in the gh and the little ones always ripen first-- this year on 3rd july ans i'm still getting new flowers & fruit, this year the bush variety is 'venus' an orange one , very compact and sweet