As long as they are yours and have no tree preservation order? you can cut them down and remove and or grind out the stumps or you can apply stump killer once chopped down.

You asked this question on 14th august and I answered it then.

Me to Steragram - thought it was familiar.

It would help if a, you could add a photo and/or b, if you stated what trees they were. Depending on if you have changed your mind re chemicals....... and what sort of trees they are. If they are of the type of weed that grows to 40+ eg ash or field maple, then cut down and spray any new foliage with glysophate, use stump killer chemicals found in GC.