Went through the process at CM last week , in and out in under 3 hours ( without any appointment)
I wasn’t asked to change documents that i produced ( which included 4 items from my bank )
A bank statement ( in my case only 6 months given as this was my first extension ,and the account was only open 9 months total )
A bank letter confirming my account balance over 800k
A photo copy of an updated bank pass book (with that dates activity )
The original bank pass book
And as I has suspected no need for any agent to be involved
thanks to all who replied