Hi Bagpuss77j
maybe for now let the past be for a while and concentrate on what you can do to help sort things out
I think someone suggested you open a new account for yourself - this would seem to be something you can do without anyone objecting - so as soon as you can go to your bank and ask them to set up a new current account solely in your name and have all your own income paid into it - also have all your own outgoings paid out only from that account, so If you have direct debits in force have those moved over - this new account will then be solely for your own personal finances
this should leave the account you are presently using with only your mum's money going in even though the account is in your name and is not a joint account (I believe this is what you mean when you say your mum has her income paid into your account)
doing all this will show anyone looking into your mum's finances that you have been acting in good faith so far but now understand there is potentially a problem and have taken sensible steps to begin to sort the situation out
there is no need to explain to the bank why you are doing all this
then just check the existing account so that all of your mum's own bills, fees etc are being and will be paid from that account - and from now on use that account to pay for anything which is specifically for your mum eg her toiletries, her clothes, having her hair done ...
then sit down with the utility bills for your home (gas, electric, water, phone, Council Tax if that is still being paid in full ...) and decide what you feel is a fair amount to have your mum contribute; look at how much you spend on food for you both, cleaning products for the house and anything else that you share the use of, and work out a fair share for your mum to pay - when you have looked at all shared expenses, then organise a direct debit payment each month from the existing account (which is now effectively your mum's) into your own new account - and that will be living expenses taken care of
at this point you will have pretty much sorted out the finances for the future
I'm wondering why you have not applied for Attendance Allowance or Carer's Allowance - look into these and if your mum are eligible for the AA, get that application filled in asap, Age UK or CAB can help you - and the extra money will be very helpful - then look into CA if you are eligible
and have you contacted your Council about a decrease in Council Tax with regard to your mum - that should be 25% off
when you've sorted out all the present finances, then start looking at what happened in the past - get/print out statements and as far as you can remember make a note next to each payment explaining what it was for and whether it was for you, for your mum (all those things you've mentioned in your posts eg new mattress, new sheets ...) or shared expenses (I'd be using 3 coloured highlighters - and not highlighting any payments I wasn't sure about to look into later) - same with income; make it clear what is your mum's and what is yours (2 more colours?)
if you have any receipts/paperwork/invoices etc, get them together in a folder
this way you are gradually working your way through everything and beginning to sort out what's your mum's and what's yours
just be honest with the LA, that way they are less likely to think there's something untoward going on - you won't be the only people they've dealt with who haven't quite got their finances perfectly organised
when you have the assessment, do ask what help is available with incontinence and mobility
sorry to have gone on - this is just what I'd do in your situation to settle my own mind
best wishes
PS this took so long to type Jessbow has asked questions - not sure now whether you have any income of your own - but I still think you need to make the account your mum's money is paid into SOLELY for HER - any purchases for her should then come from that account - she should be paying her own way (but, of course, not paying any of your personal expenses); you yourself and/or your husband shouldn't have to pay any of her bills/fees etc