I took-on a full size allotment (400sq mts) last year, & it was comptetly overgrown. I decided to cultivate half of it & put-down carpet on the rest to suppress the weeds. I also decided to grow crops that I could store...spuds, onions, beans etc. I also put in lots of soft fruit...strawbs, rasps, blackcurrents etc.
As 20 says, its a lot of hard work...but worth it in the end.
BTW, this winter I'm going to raise all the beds, & put carpet down on all the paths to keep the weeds at bay.