I think if the UK leaves the EU with "no deal", passports will require 6 months left from the date of arrival, also any extra months added if renewed early may not count (no longer applies when renewing), this only applies to EU countries. Google renewing a UK passport after Brexit, (GOV.UK), the blue passports are due in October, who knows!! I understand they will not be like the old style blue passports, no idea what will happen if we leave with a "deal", yes the cost of renewing a UK passport has dropped, as family discovered, however, renew before the passport expires, it's a pain if you don't, you have to start from "scratch", as family discovered, hope this helps.