The UK has excellent free of charge health care – it is called the NHS
(National Health Service).
All Ukrainians arriving in England will be able to access NHS healthcare free
of charge, including GP (Doctor) and nurse consultations, hospital services,
and urgent care centres.
www.gov.uk/government/news/ukrainians-fleeing-war-granted-free-access-to-nhs-healthcare 
Ukrainians coming to the UK will also be offered COVID-19 vaccines and medical screenings.
The first thing we would recommend is that arriving guests register themselves with a local GP (healthcare) practice.
This is a free service in England and they are looking forward to helping you. We recommend you go to the GP practice your host family use. These are the healthcare professionals (Doctors, Nurses and administrators etc) who will first assess you if you are ill or believe yourself to be ill.
They will either treat you or will refer you onwards (to hospitals / specialists etc) They will also check you have received the right vaccinations and may provide you with a new patient health check.
They have access to translators who can speak Ukrainian, Polish & Russian.