Murky, we agree with Quisling that everything is completely logical. To establish a value for M, we first found B - in 22D there are only two possible values of B for which the answer can be entered in the grid, and the correct value can be found using 21A. Then M can be found using 18A.
Two pairs of values for L and O can be established using 26D; the correct pair can be found using 7A.
We doubt that this pathway is unique, but it is the way we used (as far as we can see from our notes). Hope this helps.
However, Murky, having reread your opening sentence, we think your problems were possibly drink related!😉