According to my magazine BBC Gardeners World roadshow on Friday 19th August is at St Anne's in Nottingham. It is the country's largest and oldest allotment site - 70 acres.
They talk to a 76 year old man who had 9 allotments - altho now he only has 4. (Good on that man)

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Sorry not sure what time it is on but definiately one to watch if you can.