The Age UK site has some excellent advice on all matters which you will be facing at the moment.
If your paying council tax, get onto them straight away as you get a 25% discount.
Some additional advice I would pass to you, based on what has worked for the mother in law (I have to handle all that for her).
Look at your phone bills/broadband, move to a more suitable plan is available
Consider your gas and electric bills, any better deals out there?
Water meter, if your not on one get one, this saved the MIL nearly £450 a year.
Car insurance, single named person (in our case I add the wife to for added security) with a lower mileage limit, brings the cost down a lot.
Use your bus pass where possible e.g. trips into town etc.
Get any home insulation offers you can e.g. free loft insulation, cavity wall etc (if possible), replacement boiler yada yada
Enquire about funeral benefits, they are out there and all help, do a search for bereavement benefits
Check with the DWP as you may will be entitled to some of her pension if you did not accrue full stamp yourself or if she contributed into SERPS
Its amazing how much you can save per month, I know its difficult and a tough time for you but, hunting out some of the above helps as a distraction when you need it.