Place tomatoes, bbq sauce and worcestershire in a blender or bullet and blitz until well mixed.
Pour over your meat diced or whole piece (about a kilogram or so) and crock or casserole as per usual.
Taste the gravy then add salt and pepper to taste before serving.
If you feel the sauce is not thick enough add a little cornflour and water blended, stir and cook for another 15 minutes until thickened to your liking.
Notes
I personally don't bother with thickening with cornflour as once its over vegetables for us it spreads nice and it's great with mashed potato.If you do want a thicker sauce coat your meat in seasoned flour and pan fry before pouring the sauce over.Any leftover gravy pop in a labelled container and freeze for those times you like just a little tomato gravy with a steak or sausages.Of course you can add an onion and other bits and bobs to the recipe as this is only a place to start and much cheaper than the store bought mixes.