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-&gt;2, 1-&gt;3, 1-&gt;4 and/or 1-&gt;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-&gt;3, 1-&gt;4 and/or 1-&gt;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&#39;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&#39;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.