DO NOT, ever, give your drivers license as proof of identity. At least redact the photo and your signature. All they need for a SAR is a copy of your V5C which shows your name and current address. Even just the NtK is sufficient as it already contains your name and address on it.
This is not a SAR. It is a formal complaint. If you want to request a SAR (never recommended at this stage) then you email that to the DPO email address from their privacy statement.