Another question is the benefit of going for the same-day appointment ahead of posting it? The obvious one is receiving the passport back far quicker, but I was wondering what is the difference in cost with going for the appointment and posting the renewal application?
The same-day appointment gets your visa decision on the day (within a few hours) and you get your passport and documents back on the day... then your BRP card will arrive in the post within 10 days, though for many people it arrives in about 4 days.
If you apply by post, you're looking at being without your passport and visa for up to 8 weeks.
So, the benefit would be getting your visa within a few days compared to a few months... which is useful if you need to travel or you need the BRP for a job or something similar.
If you don't need the visa back quickly, you may as well save the money and apply by post, since the processing time is only about 8 weeks. In comparison the ILR application after 5 years can take up to 6 months to be processed, so there may be more benefit to applying in person for that visa instead.
Couldn't find how much it would be for extending the visa on the government website and wanting to start budgeting for it ahead of time!
The current prices are:
FLR(M) visa = £1,033... but this has been approved to rise to £3,250 by 2020 (though it may not rise by that much in that time)
IHS surcharge £500... but this will be rising to £1,000 sometime this year
In-person appointment = £610... but this also rises in April each year (last year it was £590)