Have your butcher chop the bones into manageable pieces (maximum about 3" long). Cut the beef into small pieces. Brown the bones and meat in a roasting tin in a hot oven (Mk 7 - 425ºF - 220ºC) for about 30-40 minutes turning them occasionally. Place them into a large saucepan with the water and salt. Slice the onions, carrots and celery (no need to peel them) and add them to the pan along with the bouquet garni and peppercorns. Bring the water to the boil, skim off any surface fat with a spoon, then cover the pan with a tight-fitting lid. Reduce the heat and simmer very gently for 3 hours.
Allow the stock to cool a little then strain it through a fine sieve (strainer) and discard all the solids. Allow the liquid to cool completely and then skim off the fat (which will rise to the surface). This produces about 3 pints (1.8ltr) of good brown stock that will keep in the freezer until required. A little time taken, but the improved flavours will make it well worthwhile.