You can download Attendance Allowance forms, which run to about 40 pages. Provided the need has already existed for 6 months, payment will be dated from the date of receipt of the form. Or you can ring 0800 733 0122 to ask for a dated form, in which case payment will be from the date of your call, provided you return the form within 6 weeks (and the condition has already lasted for 6 months).
Worth doing both LPAs. You can have more than one attorney, and you can name reserve attorneys in case the main attorneys die or become incapable. You can also give the name of friends or relatives who are to be told when the form is registered with the Office of Public Guardian - this is a safeguard against the person being pressurised into granting PoA.
If you have more than one attorney, you can specify that decisions are made jointly - all attorneys have to agree - or "jointly and severally" - one attorney can take decisions without involving the others. If you are all of like mind and trust each other, 'jointly and severally" offers more flexibility - you don't all have to sign when drawing out £10 pocket money for you parent, for example.
Health and Welfare LPA can only be invoked when the person has lost capacity, so it ensures you can fight their corner if they have dementia or if they're in a coma.
You can specify that a Finance LPA can be invoked while the person still has capacity - so you can, for example, take over the main bank account and major expenditure, and leave them with a bank account with a small amount of money in for pocket money.