you're probably right, but the OP is going to be disappointed if immigration offices are closed throughout January. Unlikely but possible. I think it's worth going to ask them this month.
If you explain your situation they might allow you to extend now, especially as there's the possibility of a lockdown in the new year. Making you wait until January to extend benefits nobody.
I don't agree with the "10 days to a week" advice. People can't live their lives not knowing which country they'll be living in a week's time. Plus, rushing to buy flights is never fun and is usually expensive.
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