Not clear where you think 90 days comes from - you may be confusing it with the requirement for min. 90 days consultation occurs before >100 redundancies are likely to be declared. This is nought to do with that.
Irrespective of what your contract says (one month) I reckon that on a change like this, the employer has to give you at least your statutory notice period - and that for you is 10 weeks notice (one week per full year of employment).
However as it is a fundamental shift, there should be meaningful consultation going on, on an individual basis. Say, for example, your life revolves around doing something in the earlier evenings, they should take that into account before imposing such a change on you. Doesn't mean it can't happen. The test, of course, of whether they've done this fairly would be at Employment Tribunal, though that's no help to you.
It seems a pity that Canary42 bothers to utter an answer, as he seemingly knows nothing about employment law.