1. A sulfated oligosaccharide, having the general formula I: R1-(Rx)n-R2.(I) wherein R1 and R2 and each Rx represents a monosaccharide unit, all of which may be the same or different, adjacent monosaccharide units being linked by 1->2, 1->3, 1->4 and/or 1->6 glycosidic bonds and  n is an integer of from 1 to 6, provided that polysaccharide is not a compound containing 1-4 linked glucose residues. 2. A sulfated oligosaccharide according to claim 1 wherein n is from 1 to 4, preferably 3 or 4. 3. A sulfated oligosaccharide according to claim 1 or claim 2, wherein the monosaccharide units are hexoses selected from the group consisting of fructose, glucose, mannose, altrose, allose, talose, galactose, idose and gulose. 4. A sulfated oligosaccharide according to claim 1, having the general formula II: Ry-(Ry)n-Ry.(II) wherein each Ry group is the same and each represents a monosaccharide unit, adjacent monosaccharide units being linked by 1->3, 1->4 and/or 1->6 glycosidic bonds; and n is an integer of from 1 to 6 provided that polysaccharide is not a compound containing 1-4 linked glucose residues. 5. A sulfated oligosaccharide according to claim 4, wherein n is from 1 to 4, preferably 3 or 4. 6. A sulfated oligosaccharide according to claim 4 or claim 5, wherein Ry represents a  monosaccharide unit which is a hexose selected from the group consisting of glucose, mannose, altrose, allose, talose, galactose, idose and gulose. 7. A sulfated oligosaccharide according to claim 6, wherein Ry represents glucose, mannose or galactose. 8. A sulfated oligosaccharide according to claim 1 or 4, wherein the oligosaccharide is a naturally occurring oligosaccharide. 9. A sulfated oligosaccharide according to claim 8, wherein the oligosaccharide is selected from raffinose and stachyose. 10. A sulfated oligosaccharide according to claim 1 or 4, wherein the oligosaccharide is prepared by enzymatic or chemical degradation of a naturally occurring polysaccharide. 11. A sulfated oligosaccharide according to claim 10, wherein the oligosaccharide is a compound from chondroitin or expopolysaccharide prepared from the diploid yeast Pichia holstii. 12. A sulfated oligosaccharide according to claim 11, wherein the oligosaccharide is selected from chondroitin tetra-, hexa- and octasaccharides. 13. A sulfated oligosaccharide according to claim 11, wherein the oligosaccharide is mannopentaose phosphate from the yeast Pichia holster. 14. A use for the anti-angiogenic, anti-metastatic and/or anti-inflammatory treatment of a human or other warm-blooded animal patient in need of such treatment, which comprises administration to the patient of an effective amount of at least one sulfated oligosaccharide according to any of claims 1 to 13. 15. A use according to claim 14, wherein the treatment comprises treatment of an angiogenesis-dependent disease, including angiogenesis associated with the growth of solid tumours, proliferative retinopathies and rheumatoid arthritis. 16. A use according to claim 14, wherein the treatment comprises treatment of inflammatory diseases and conditions in which the heparanase-inhibitory activity inhibits leukocyte infiltration, including chronic inflammatory diseases such as rheumatoid arthritis, multiple sclerosis, insulin dependent diabetes mellitus, diseases such as ulcerative colitis and Crohn's inflammatory bowel disease, allograft rejection and chronic asthma. 17. A use according to claims 1-13 for the anti-angiogenic, anti-metastatic and/or anti-inflammatory agent in the treatment of a warm-blooded animal (including a human) patient. 18. A use according to claim 17, wherein the treatment comprises treatment of an angiogenesis-dependent disease, including angiogenesis associated with the growth of solid tumours, proliferative retinopathies and rheumatoid arthritis. 19. A use according to claim 17, wherein the treatment comprises treatment of inflammatory diseases and conditions in which the heparanase-inhibitory activity inhibits leukocyte infiltration, including chronic inflammatory diseases such as rheumatoid arthritis, multiple sclerosis, insulin dependent diabetes mellitus, diseases such as ulcerative colitis and Crohn's inflammatory bowel disease, allograft rejection and chronic asthma. 20. A pharmaceutical or veterinary composition for anti-angiogenic, anti-metastatic and/or anti-inflammatory treatment, which comprises at least one sulfated oligosaccharide according to any of claims 1 to 13, together with a pharmaceutically and veterinarily acceptable carrier or diluent therefor. 21. A medicament for the anti-angiogenic, anti-metastatic and/or anti-inflammatory treatment of a human or other warm-blooded animal patient of at least one sulfated oligosaccharide according to any of claims 1 to 13.