Funeral arrangements specified in a will are not binding upon the family or executors of a deceased person.
For example, my will states that my body should be cremated without ceremony and my ashes disposed of, also without ceremony, in any convenient refuse receptacle. That doesn't prevent someone from having my body buried, with a religious ceremony, after a funeral in St Paul's Cathedral with hymns from the Vienna Boys' Choir and music from the Berlin Philarmonic Orchestra! ;-)
This quote, from the Help the Aged website, might be relevant:
"If there is no money to pay for the funeral, the local council should arrange and pay for a simple funeral (or sometimes the hospital will do so if the person died there). This will be a dignified funeral followed by cremation or burial, and is not like the old 'pauper's' funeral."
Source:
http://www.helptheaged.org.uk/en-gb/AdviceSupp ort/HealthAdvice/Issues/Bereavement/as_bereave m_240206_4.htm
Chris