Bumpy lawn

I'm not sure if this is the right place to post this or not but I'm looking for some advice with an extremely bumpy lawn. I moved in with my girlfriend about 6 months ago and the lawn is in a terrible state. It's a housing association property and she is a single mum so it has not been maintained properly. I've managed to get most of the weeds, brambles etc under control but the lawn is still giving me issues. It is so uneven, with random holes everywhere and big ant mounds etc, you name it it's there! It makes it such hard work taking a mower over it and had even lead to me having to get the blade replaced from hitting unexpected items. So I'm trying to find the best solution to levelling out my lawn. My theory was to rent a rotavator and take that over it ( it's a fairly large garden). Is this a feasible idea? Will it fix my problem? How is it just a case of taking a rake to it after using the rotavator to make sure it's all level again and then planting new plant seeds? Assumingly this plan would also rid is of the random nettles and brambles popping up. Is there a better solution than this? All ideas welcome!