As per new process you need originals of everything including british passport along with a self attests photocopy.
The keep originals and will send it back to you in a week.
The OCI comes around 3 to 4 weeks after that.
You need 2 envelopes ( one for returning originals and one for OCI)
But if you are applying in birmingham jurisdiction then they will make you pay for 2 courier envelops at the time of application
My suggestion for you is to apply for an evisa which can be processed within a few days and you only need to send scanned copies of documents.
Do it now as then you do not have to then wait for the OCI to come and then get stressed .
A 5 year multiple entry evisa to India is only $80 ( 80 USD) .
In fact if you dont need to do any financial deals etc while visiting Indiaa and if it's a short trip you can go on an evisa and then come back and apply for oci.
Just make sure that someone is at home when oci arrives if you decide to apply and go for a long trip to india .
Make sure that you apply for evisa on the real site at
And be careful as there are many scam sites