Visitor visa for marriage queries.

[hurrimark]

- Does my partner need to be in the UK for the 7 days before we visit the registry office or can I give notice myself and she can come after the 15 days has elapsed?
It makes it awkward with job/work if a minimum of 23 days NEEDS to be taken before the actual ceremony.

- How long before the actual wedding day should one apply to obtain the visa?

- Are there any agents that can help the partner fill out the online application
form if their first language is not English? Also the additional documents, are they all attached via PDF through visa4uk online application?

When i try to register 'applying for someone else' on visa4uk website, entering my partners nationality as 'Taiwanese' it says this:
IMPORTANT! Only customers who hold a Tier 5 Youth Mobility Scheme Certificate of Sponsorship (CoS) issued by the Taiwanese Youth Development Administration should proceed to submit an application under this category
I don't understand?

Thank you very much for any guidance on this confusing topic.