Passport renewal should allow time left to be added to new passport, as it was before 2018. Many countries incl EU need 6 months minimum left on traveller's passport. The change in Sept 2018 means many passport holders lose 6 months + therefore passport is not for 10 years, but 91/2 years.
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Money saving experts & many other travel professionals have highlighted this & have lobbied the Home Office to get 'carry over' (of up to 9 months) reinstated.