help please

Hello,

I am looking for some advice.
I am british and my partner is african and he lives in Africa and i live in the UK
we are looking to marry in the UK because its far cheaper, and since all my family live there...it means they dont need to pay for visas to come here( british nationals need a visa to come here), aswell as 300 per person in flights and hotels on top...its just too much.

so like i said we intend to marry in the uk but not stay here...i will return with him after marrage to Africa.
So through a friend i found we need to give notice of marriage, and to do that he needs to obtain a marriage visit visa.

im struggling with some of the proofs they ask for...as we intend to marry but return to africa after the wedding....

theyre askin for proof of booking but how can i do that if i cant give notice and there will be a 70 day notice period so i cant book anything anywhere until we given notice. so how is this meant to work?