According to the bumf on the e-bay page it belongs to Major Kenneth Jan David Hume MBE, The Royal Welch Fusiliers (MBE awarded in the Queen's Birthday Honours 2000). He was awarded the Queen's Medal in 1988
In this case it was stolen, but I have seen medal sets at Militaria Fairs (I collect insignia not medals by the way) and in many cases it is because the winner/recipient has deceased and the family decide to sell them on. Many reputable dealers check new medals to the market on the police lists which are distributed.
The number of Falklands, Gulf and modern medal sets I have seen does annoy me at times, but even the holder themselves sometimes sell them on for a bit of extra money, as not every serviceman is lucky to have a very well paid job.