The Alzheimers Society have a great helpline and can help you with all sorts of issues and local services 0300 222 1122
As does Age Uk, their helpline is open 24 hours 365 days a year and they give excellent practical advice and is a freephone number 0800 169 2081 so you can get hold of them at a time convenient to you.
I think I would get the hospice involved to support your Mum (and your Dad) and that would probably be my first call because if you have a good local hospice they will help you to coordinate things. They have some fantastic services.
It might be useful to involve Social Services if they are not already - an assessment and help with care. Adult Social Care duty desk will give you some advice about the way forward and they can do a carers assessment at the same time
Your mum will be eligible for speedy Attendance Allowance to help with extra costs, as is your Dad if he is not already getting it. Worth checking this and asking for help with the form filling - sometimes your local carers organisation will help with this but usually AGe UK will send a volunteer to help with this if you want them to - they are experienced form fillers and it takes the stress away
Although your Mum has just had a shock diagnosis and so have you all................I suspect she will still want to be very much in control of your Dad's care. Take care of yourself as you tread this delicate balance. There is lots of help 'out there' and lots of help and support on here too xxx