A Letting Agent Is Trying To Charge Me £150 For Tidying Up A Garden Which Was In A Poor State When I Moved In And Has Since Been Tidied By Me. I Have Moved Out. Should I Have To Pay?

I did not get an inventory when I moved in and the garden was full of weeds in the lawn and borders and the bushes were overgrown. I've since tidied the garden and cut the lawn regularly. Now I've moved out the letting agent is withholding my deposit and asking for £150 to get rid of lawn weeds, cut the grass and prune bushes. Can they do this?