We had to accept our secondary school place by letter. Our official letter was from LEA, return the slip that says you accept place. We also had a letter directly from the school, which we had to post a reply slip.
Do you get a receipt/confirmation/acknowledgement or anything? I was just wondering that if your acceptance slip was lost in the post, you wouldn't know would you? We got proof of postage for the letter, but still.
Whether or not you will get any kind of acknowledgement varies from LA to LA (and even from school to school within an LA). If your acceptance has gone astray you will receive another letter from the LA encouraging you to accept the offer and setting a new deadline for acceptance.
Maybe it is different from LA to LA. I accepted my dd's place by email instead of any official form and I had a reply email from my LA to confirm they have updated my dd's record. In my acceptance email I stated all my dd's name, dob, school name, home address, secondary school name etc.
I didn't think I could do it via email. I did my school choice form by post and received the place allocation via post so couldn't accept the place online. So I rang the LEA and their staff suggested that I do it via email.