40% of all Bitcoins are owned by just 1000 individuals.
This gives them a disproportionate amount of control over the market as they are able to dump them at anytime.
This is not to mention the high proportion of bitcoins held by miners and exchanges, who may have perverse incentives to ensure that as many people buy up bitcoin as possible and hold it for long enough for the price to rise.
Is there any way to deal with the high degree of centralisation that Bitcoin has?
You should pick a better term since people usually mean "centralization of the network" when they speak of Bitcoin centralization.
Not agree! Just because some people have more Bitcoins than others does not mean the centralization of the market.