Instead of adding water to diloute tomato puree try using the juice from a can of fruit cocktail,it makes a good bit of difference taste and smell wise,i used aldis brand,it is not syrup its like water and not over sweet,i honestly think you will be glad you tried it

Interesting suggestion, MP.  Last night I ate steak-and-kidney pie with chips, and as I had slightly over-cooked the latter, I looked for some tomato ketchup with which to soften them.  Sadly I appeared to have run out, so I tried passata