Living in Scotland but getting married in England.. confused on giving notice!

Hello
We're due to get married next July, we both live in Scotland but are getting married in our Hometown in Devon, England. The whole giving notice is confusing me and giving me a headache... I was hoping someone who has been through this before can give me some advice.

I'm planning to give notice in England as I know I need to do a residency there for 9(?) Days prior and my parents will write a letter to say that I have been living with them. Can I do this at any time? For example I am going home for a short holiday in Feb so was going to give notice then?
Then my partner will give notice in Scotland near the end of April as that's within the 3 month timescale of Scottish law.
Or do we both have to give notice in April?
I'm just so confused and even the info I've read online or got from the registrars don't make sense 😭