Your plot looks really good, you're not having waist high brambles and grass and weed to tackle, as above cover what you can with dark plastic, or weed membrane, Old carpet may not be allowed on your site and it is a pain anyway, I inherited half a plot load and the weeds had grown over and through it!
Plan where you are going to place the shed and composting area, taking into account not shading other peoples plots and where most people have placed their sheds, you are going to want to store tools and have somewhere to get out of the rain.
Decide if you are going for 2.4m x 1.2m beds with paths around or clear the whole plot every year person
Personally for me the allotment is easier to control in beds, with 600mm paths all round so that there is room to get down on your knees. I don't have to battle every year to get on top of the whole thing as the path structure removes a significant area of land that has to be dug and weeded each year. You can cover beds with weed membrane for the winter to stop weeds in the early spring.
Consider a diary on here to record progress and to use to review past performance and plan for the future, you also set up a comments thread and get guidance. Take a look at mine at
http://chat.allotment-garden.org/index.php?topic=100234.15 from when I took mine on and you will see that after clearing and erecting a shed, I dug one bed at a time and my first plantings were 4 beds or potatoes
I hope you do decided to keep a diary with many photographs and we can watch your progress, and comment and provide guidance when requested.