In the UK, primary and secondary public schooling are free. This is up to the age of 16 years. A-Levels are the next stage of higher education that follows secondary education and are hosted by sixth form’s or colleges. Most secondary schools have a sixth form so students naturally progress onto this. Those who do not wish to pursue A-Levels can decide to either pursue a professional career, apprenticeship or other college courses. It is normally advised to still continue onto higher education as this enables the individual to have better professional prospects. For those aged 16 - 18 years pursuing any type of higher education, the sixth form and college will not charge and is therefore free. A-Levels can be completed by senior/mature students but this would then incur a cost by the college. These are guidelines of public sixth forms and colleges. Private schooling at any level will always incur a cost and will be dependent on the educational institution.
University charges are the same regardless of age of entry, for a standard degree you are looking at £9650 per year, this is higher if you are pursuing certain degrees like medicine, however as a UK national or permanent resident you are able to apply for publicly funded loans to cover the education costs, which would then be paid back in small amounts once you start earning a certain amount. If you have any dependents that are pursuing university but you and them have not yet achieved permanent residency then they will be subject to international student fees, and will not be entitled to public funds to support their studies.