How to remove 10-20mm of uneven concrete from a rear extension floor

You could contact a local tool hire centre regards hiring a floor grinder / scarifier. Tell them what you are wanting to do and they can advise you on available plant. Be careful not to reduce slab thickness so as to undermine its strength / capability and always be aware of any inlaid services within the concrete be it pipes or cables. Alternatively if appropriate to suit other floor levels you could apply a self levelling laytex on top of existing floor to level out. Regards David

You can remove uneven floor by breaking the floor up with a kango but if you want the floor to be even you can self level the floor.it depends on what you need but there is a solution for what you need