If the flowers are falling and no fruits forming then this means that the tomatoes have not been pollinated.
Are they in a closed greenhouse where no insects can get in? If so, you will need to do the deed yourself with a small paintbrush, twidling it arround in each flower in turn without cleaning it of pollen.
Are they in the open garden? This year has seen a great reduction in the number of insects around due to overuse of chemical sprays and with the late spring contributing. Again, you will need to do the pollinating yourself.

Thankyou, i will pass this on to robbie, its great to have this knowledge available as i have only a little gardening experience.agi

It also helps to wear a yellow and brown striped rugby jersy and say buzz-buzz at the same time ;-))))))
(ps My first post was serious.)

I find tapping the plants gently, also make sure the air is not too dry on hot days, damping the gh floor can help

tomatoes are self pollinating.....no insects are needed.
Any problems setting fruit are usually because temperatures are too high, not enough water.
No need to use a paintbrush. A little shake of the plants will help pollination should you feel the need, but that won't aid setting of fruit.