Now that six allotments have been allocated to six old village residents, this is a great website for advice. https://www.nsalg.org.uk
These three extracts from the Association website are very useful.
Below is an extract on how to obtain allotments for those wanting one.
National Allotment Society member sites can also advertise plot vacancies on this site click here to view the page. Click here to read the NAS leaflet “Obtaining an allotment and what you can expect”.
Other allotment sites are provided by private landlords, including organisations like the Church of England. Hunt out your local allotment society and ask them if they know of any available plots or who manages the land which they use if it’s not owned by the local authority.
If there appears to be no allotments in your area, then we recommend you find five like minded people who would like an allotment and are on the electoral roll or registered council tax payers. Then individually and collectively, submit a formal letter to the local council. Send one (you can put all six letters in one envelope) by recorded delivery and one hand delivered, with at least two witnesses present. All local authorities have a mandatory obligation to provide allotment provision under Section 23 of the 1908 Small Holdings and Allotments Act. (But be warned there is no time scale attached to this process and unfortunately this process cannot be used in London, as the rule only applies outside of the capital thanks to the London Government Act 1963.) The Society recommendation is that authorities should supply 20 plots (or .5 hectare) per 1,000 households.
If you have no luck with the local authority and established private landlords, then your next step might have to be a sideways one… look around your neighbourhood and see if you can spot any vacant land which would make a good allotment. Find out who owns the land and ask away, it might just be possible that you can use it for growing on.