My initial first claim (4 years ago ) took a good while to be finalised, but everything owed was back dated.
When my MS worsened last year I told DWP that my condition had changed, I was then reassessed at home about 4-5 weeks later and all the paper work was finalised about 2 weeks after that.
Reading the above posts it looks as though things have improved in the time you have to wait ?
Mine came within 2 weeks , to help me fill in the forms I saw the benefit lady at our local MS centre in Norwich , she was a great help with filling in the forms and put down things I would have not thought about putting so if you can get help it is well worth it. I ended up with basic on both parts.
Mine arrived within about a week. I got my decision about two weeks after my face to face assessment. The whole thing start to finish was about five weeks. I got top rate for both which was more than I had been getting, but only for three years whereas I had DLA indefinitely.
I deal with lots of PIP queries in my voluntary work at CAB and you should get the form within a week, you then have 28 days to complete and send back to DWP. If you are struggling to meet the 28 day deadline you can contact DWP and ask for an extension which, whilst they may grumble, they invariably grant an extension. The CAB website has some really useful information around PIP and how to complete the PIP form. It is a tricky form to complete and most CAB’s do provide help to complete the form and I would highly reccomend getting some knowledgeable and experienced help when completing the form.