Is my section 21 valid?

I (or rather, my agent) issued a section 21 notice at the start of a tenancy which has since rolled over to a Statutory Periodic Tenancy.

Unfortunately the letter was issued with the tenants name misspelled.

He wants me to issue a new section 21 (with two months notice) rather than leaving in a month's time as requested.

Is he right that the s21 is invalid because of the error? Should he have told me that the details were incorrect at the time?

I know why he wants to push the date back (and it's reasonable) but I need the place back asap for my own (also reasonable) reasons!

Thank you for your help.