Does anyone have any experience of doing this? Is the process the same?
Lots and lots of people have experience doing it... a large number of people who are applying for their second visa will have different financial circumstances compared with their first visa

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The income you have between now and the last 6 or 12 months of the visa is not relevant... all that matters is that between you, you meet the requirement in the final 6 or 12 months before you apply for the next visa.
So, the only difference is in whose income you fill out on the form when you apply for the next visa:
- if the sponsor's income is over £18,600 and they meet the requirement using only their salary at the time of applying, then they only fill out their income details and only provide their income documents
- if the applicant's income is over £18,600 and they meet the requirement using only their salary, then they only fill out their income details and only provide their income documents
- if you need to combine both your salaries to meet the £18,600 requirement, then you fill out both your employment details, and each provide your own set of financial documents.