Strawberry jam

Today I made some strawberry jam. I used the bread maker as I'd noticed a recipe in the booklet and thought I'd give it a go. The resulting jam was a nice colour and the fruit distributed well, however it is slightly more runny than I would ideally like. I'm not surprised though, as from what I've read, strawberry jam is notoriously hard to set and very easily spoils if you over cook it.
Anyhow, the recipe was 500g strawberries hulled and halved (I quartered most of them as they were a bit big), 1 1/2 cups sugar (I used vanilla sugar) and 1/4 cup jam setting powder (a premixed sachet containing glucose, pectin and citric acid). This quantity makes 3 small jars (I filled a small 200g jar, and 1 1/2 larger jars (300g).
I've got a few other recipes to try, some using lemon juice. The strawberries have slowed down a little with their fruit production right now, so not sure if they just need a boost of liquid fert. or what. Some plants are also starting to put out runners which I guess might account for the drop off in fruit. Any ideas folks? Should we pick off the runners now or later? (we want to get more plants going).