We successfully applied for PIP about 3 years ago. It all went very smoothly. Some items on the assessment were marked lower than expected (my wife could still talk the talk) and others higher but they balanced out.
I applied on behalf of my wife as I have Power of Attorney. This took a few extra days for them to register it but (if I remember correctly) any payment given is backdated to the day of the first phone call. I was with my wife during the interview and the interviewer asked my opinion on most questions after my wife had given her answer.
The thing to remember about PIP is that it is given for the effect of an illness on your and your OH's life, not on a diagnosis of the illness. So just having a diagnosis of Alzheimer's isn't enough, you have to show that there are things your OH has difficulty doing and give examples.
I found the best way to do this was to keep a diary over 3 (bad) days - the headings for the diary were with the online application form. I made a note at the top of the diary that I had written it but it was presented from my wife's point of view. To some extent you need to stand back and write the diary in a very factual way, this is where the Alzheimer Society or CAB may help.
For example under "Dressing / Undressing" we put "Needed help to decide what to wear. Dressed myself except socks and shoes. Needed reminding to put on glasses and hearing aids. Undressed myself at night". Best to be completely honest (helps you at the interview) but don't be afraid of putting in trivial issues. Include all the times your OH gets confused, forgets things or needs help.
@sarahsea I think you've got all the relevant symptoms in your paragraph starting "So, this is the problem" but instead of "he cannot recognise people" you'll need real examples such as "We met X in town today, OH has known him well for 5 years but didn't recognise him". Keep a notebook for a few days and every time something happens write in the time, place and a one sentence description of what happened. Don't write too much and don't try to go back to refine notes afterwards. After week go through the all notes and you'll have the basis of your diary.
Even if you can only get the minimum level of PIP apply before your OH is 65 as PIP is more than Attendance Allowance. PIP continues after your OH is 65 and can be reassessed at any age.
Thank you BeardyD, I already keep a diary and I can think of many examples which would support the application and demonstrate the impact of the illness on my husband's life. I'm sure I could pull out some notes which I could use. When you live with someone with a progressive illness, you don't always recognise the daily difficulties as they change (get worse) over time. For example, if someone asked me if my husband can dress himself in the morning, I would probably say yes, but in reality, he often asks me what to wear, which trousers fit him, he puts dirty clothes back in the wardrobe instead of in the laundry basket, so gets in a muddle re what's clean, can't find his socks etc. It can take a while and I often have to support him.
I think I am beginning to understand how the information has to be presented. Thanks again for such a helpful reply.