Hi,
We got married in the UK (fife) having lived in Sydney in the lead up. I can't remember all of the ins and out of giving notice however it was no problem for us. Either my parents picked up the form or we requested it to be sent to them. They filled it out and sent it back (or they send it to us to do and then send back) with birth certificates. As long as this was back to allow for the correct amount of notice time then thats fine. About 4 days before our ceremony we went to pick up the actual marriage certificate - this was the part we had to do in person. After the ceremony we dropped the signed certificate back at the registry. Our marriage certificate (and extra copies) was sent to us in Sydney a few weeks later.
Sorry some of the details are not super clear, I just wanted to reassure you that you it can be done and you won't need to be back in the UK for weeks before the wedding. I'd recommend contacting the registry direct.
Good luck