There is good evidence that radiotherapy is effective in halting the progression of dupuytrens disease. Unfortunately in the UK, despite NICE approving the treatment, the shortage of resources means that there are no NHS centres to my knowledge treating Dupuytrens.

In London private radiotherapy services are available at three hospitals: the Cromwell Hospital, The Harley Street Clinic and the
Parkside Oncology Clinic.  The London Clinic is also building a new cancer centre, which will include radiotherapy. Most NHS services will offer private radiotherapy and it might be worth enquiring about this avenue.

Dr Shaffer is another contact who tells me that he is a consultant clinical oncologist working at Royal Surrey County Hospital, Guildford.
Although he only see patients in Guildford or Elstree (North London), He is able to treat in Little Aston, Portsmouth, Southampton (as well as Guildford and Elstree). His secretary's details are: , Tel No:      01483-442598

The big problem if you are paying for it yourself is knowing whether you will benefit. The vast majority of Insurers are now covering Radiotherapy. For them it is a clear winner. Pay for radiotherapy now and not have to keep paying for the treatment of Dupuytrens over the next 10 years.
If you are somewhat older and develop a nodule then probably you will not develop serious disease and radiotherapy is not worthwhile. Conversely if you are 25 and already have nodules starting I would consider radiotherapy almost mandatory. Where you fall between these two is up to you. I would also consider radiotherapy if I had more than 2 living relatives with the disease or if I had had surgery, NA or fasciectomy, and had had recurrence of the contracture within 12 months.