There are different ways to apply for British citizenship, including ‘naturalisation’. Check your eligibility to apply.| GOV.UK
Providing your biometric information and supporting documents for visa and immigration applications within the UK; UKVCAS service point locations; cost of appointments.| GOV.UK
Get a free permit to join family from the EU, Switzerland, Norway, Iceland or Liechtenstein in the UK - check if you’re eligible, documents you need to apply.| GOV.UK
The UK Embassy in Madrid says British citizens with Spanish green certificates will be exempt from EES and ETIAS travel requirements.| ETA for the United Kingdom