The things about marestail is that it's not a particularly vigorous or big plant. Event if you've got it, it won't really outcompete anything unless ignored completely. It takes about 10 minutes once a week to walk from one end of my plot to the other pulling out the worst bits and even that has a noticeable effect on it from year to year, seeing it slowly reduced.
I wish it was 10 minutes from end to end Simon. I'm loosing an hour a night picking and I'm still not getting it all.
This is my corn and broadbeans post de-weeding. You can see the bit behind them, that was pulled a couple of days before and its back.
The bottom right of the picture is the carrots which I had to leave but never took.
Ouch, that looks like hard work. I certainly didn't mean to make light of your efforts! I made the decision to build raised beds when I got my half plot, apart from one area that I use for squash. It's been the best choice I ever made. The beds are more productive (in my experience) than open ground so you don't lose any growing space and they're easy to week as you can get to every part without treading on the soil.
The first couple of years on my plot there were weeds popping up all the time, due to it having been very overgrown with flowering weeds when I took it on, mixed with horsetail in abundance. Before I grew anything I sprayed the lot with glyphosate. Then I waited three weeks and did it again. I spent hours pulling all the horsetail. After that, it was easier to keep on top of the emerging weeds and now, four years later it's possible to leave the plot for days at a time and come back to nothing more than baby weeds that aren't ready to flower and a few sprigs of horsetail
I guess what I'm trying to say is that the hard work now will pay off in abundance later on and you'll look back and realise it was worth it. Good luck.