Johnstone's aqua gloss over oil

Hi guys need a bit of advice. Just bought a house that needs a bit of TLC, all the woodwork has been finished in an oil based gloss but it's been poorly finished / lacking another coat. Would I be able to put jonno's aqua wb gloss straight over it after some prep or would I need to coverstain it first? It'll be my first time taking this approach as usually use o/b.

Cheers