Useful information on GOV.UK on catch-up immunisations for individuals from other countries and there is also an UK-international immunisation schedule comparison tool:
UK and international immunisation schedules comparison tool - GOV.UK (www.gov.uk) (this only covers the 21 countries that most people moving to the UK come from)
Unless there is documented or reliable verbal vaccine history, individuals should be assumed to unimmunised and a full course of immunisations planned. If they are part way through their immunisation then they should be transferred onto the UK schedule and immunised as appropriate for age.
There is an equivalent algorithm for screening: