Thanks for responding Bower
Yes it is a heart and it DOES look as if it's dying which is why I made allowances and planted it out.
My photos aren't the best unfortunately, but I took a magnifying glass and inspected the plant tonight. The leaves are definitely deformed and many have holes in them. It's interesting that many of the deformities are the same in several leaves, and the holes in them are in the same places too! I really don't think it's due to insects, even though I do have flea beetles and a bit of Septoria just to make it more of a riddle.
The flowers look ok with no brown in them and the fruit looks great so far.
I'm very worried that it could be Tomato Mosaic Virus!!!
Linda