Place the shallots, carrots and garlic in the slow cooker.
Spray a large frying pan with low calorie cooking spray and place over a medium heat. When the pan is hot, add the turkey joint (still in it's netting or tied with string), and seal and brown on all sides, including the ends, for 3-5 minutes.
Transfer the browned turkey joint to the slow cooker and place on top of the vegetables.
Dissolve the beef stock cube in the boiling water. Mix together the hot beef stock, red wine stockpot, redcurrant jelly, balsamic vinegar, Dijon mustard and tomato puree and stir until dissolved.
Pour the stock mixture into the slow cooker over the turkey and add the fresh thyme sprigs, rosemary sprigs and bay leaves.
Place the lid on the slow cooker and turn on to the high setting for 3-3 1/2 hours.
After 1 1/2 hours, lift the lid and baste the turkey joint with the cooking liquid. Don't be tempted to lift the lid any more than this, as each time you do it will extend the cooking time by another 30 minutes. Replace the lid and continue cooking for a further 1 1/2 hours.
After 3 hours, insert a temperature probe into the thickest part of the turkey joint to check that it has reached a high enough temperature to ensure that it is properly cooked. It should read 70ºC for 2 minutes. The juices should run clear, there should be no sign of pinkness and the turkey should be piping hot. If these recommendations are not met, put the lid back on and continue cooking for another 30 minutes, then repeat the checks until you are sure that the turkey is properly cooked.
When you are sure that the turkey is cooked, remove it from the slow cooker using a large slotted spoon, remove the netting or cooking string and place the joint on a warmed serving plate.
Carefully remove the shallots and carrots from the slow cooker using a slotted spoon and arrange around the turkey joint. Cover with foil and keep warm while you make the gravy.
To make the gravy, strain the cooking liquid from the slow cooker, through a sieve, into a medium saucepan, discarding the herbs.
Mix the cornflour with the water to form a lump free liquid. Place the saucepan on a medium heat, and stir the cornflour mixture into the cooking liquid. Bring to the boil, reduce the heat and simmer, stirring well, for 4-5 minutes or until thickened. You can use a little more or less cornflour mixture at this point, depending on how thick you would like your gravy. Taste the gravy and season with salt and pepper if needed.
Place the redcurrant jelly and mustard in a small saucepan and warm through until just melted, stirring until smooth. Brush over the turkey just before serving and garnish the plate with a few sprigs of fresh thyme and rosemary.
Pour the gravy into a jug or gravy boat and serve at once with the turkey joint and vegetable garnish.