An excellent time to get an allotment. No pressure to do anything apart from clearing and ground preparation. Weeks of good weather to gently clear and area at a time, with no pressure to show results. I have 2 allotments - one which I acquired in late July, so spent a lot of time building compost bays and mostly clearing,/spraying, while my second, next door allotment became mine in February, when I promptly did a quickie dig-over and started planting. 20 years on, I am still plagued by couch and bindweed in the 2nd allotment, while No.1 has remained clear of rhizomatous thugs. I did, however, spray the first allotment because it was a nightmare of pernicious weeds which digging utterly failed to alleviate (Bindweed can put down 20ft roots and is perfectly able to survive for years, even underneath corrugated metal covering). I know there will be scowling, but I considered it was worth getting a herbicide in over the autumn and hitting the weeds hard...which I also failed to do in my 2nd plot.
How you proceed now depends on what you are wanting from your plot. I am a flower grower and a plants-person, so the annual clearance appropriate for vegetable growing was not where I was at at all. While you may well be able to maintain a plot without needing an initial herbicide treatment, it was totally not an option when growing perennials and permanent shrubs. I also have a pond on my plot, which is surrounded by vegetation but has never successfully acquired resident frogs. (although I do have toad hibernaculums). I have never managed to persuade breeding amphibs...largely, I think, because the sheltered, enclosed aspect has encouraged birds to feast on frogspawn. My neighbours pond, in an old bath, but much more open and exposed than mine, has tadpoles every year. I really should consider removing some of the vegetation around my pond (but the huge wild roses, hazels and apples would be a nightmare to chop down).