Hi you need quite a few forms cop1 cop1d cop12 cop24, if you are already deputy, if not you'll need to fill in additional cop24 as a statement to apply to be a deputy.
I have just done this application last week.
I have been deputy for 5 yrs and last yr did a COP application and made a statutory will.
The fees are £371 each application
You will need either the original Cop3 document from your existing deputyship if you are one already to prove lack of mental capacity. Or if your relative is in care they should have a DOLS ( deprivation of liberty order) the court will accept either to prove they can't live independently at the property any longer even if it wasn't sold etc.
If you need any help, just ask, after dealing with the COP over the last 6 years for 2 deputyship a will and now a trustee and sale order I'm considering myself a bit of a expert 😉 lol