When a loved one dies there are a lot of decisions to be made and official notifications to be done. All at a time when you are least able to think straight. If you have a friend or family member who can carry out these tasks with you it will make things a lot easier for you. Your Funeral Director will be happy to help and advise you of the immediate requirements. In addition you can find useful information on GOV.UK which will lead you through the process of registering a death, notifying appropriate government departments, dealing with benefits, pensions and taxes etc. and dealing with the estate and probate.
There may be other organisations that you need to notify, for example Bank, Building Society, Solicitor, Insurance Companies, Pensions Companies, DVLA, Local Council, HMRC, Passport Office etc. Make sure you get the help of a trusted friend or family member to avoid extra stress.
The Money Advice Service is a useful source of information.