That is my exact situation. The marathon I was training for should have taken place in June, but was then postponed to October. I restarted the marathon training plan because the hard stuff isn’t actually that hard, and the long runs aren’t really that long in the first weeks. I will follow the plan until I have 18 weeks left, and then I will restart the plan.
I too was in the same boat as probably many. I was doing the Half Marathon Level 2 and did a restart but after reading a reply on the forum have taken a different approach.
I’ve dropped onto maintenance and trying to improve my VO2 by training in the top end of the range given and while it feels it’s a bit of a resting state compared to the previous training but I will start my marathon level 2 training 18 weeks to the event I have (at this stage) in November being a bit rested and better for it I hope.