Skin the tomatoes and chop coarsely. Peel and finely chop onions and crush garlic. Put into a preserving pan or large saucepan and simmer for about 15 minutes. Add vinegar, mustard, salt, mixed spice, cayenne and paprika, mix well and simmer for about 1 hour. Add sugar and heat gently until dissolved, then boil gently for a further 15 minutes. Pour into hot sterilized jars and seal.