Prior to the above dates Wales was using the patronymic system of naming, eg. Evan Ab Evan (Evan the son of Evan, or "vench" meaning daughter of). Whilst the lowlands of Scotland used recognisable surnames before the 16c, it was not until the 16c - 17c that most highlanders adopted the name of their clan chief. However, it would be quite wrong to think that we have a guaranteed way of tracing or ancestors back to the 16c, I wish!
Unfortunately, the Scottish showed their admirable resistance to "government interference" and most of their 900 parishes kept, at best, only partial records until just before 1854. These may be found at Scotlands People. In England between 1653 and 1660 the keeping of records was transferred from the churches to a civil office, confusingly, also know as the "Parish Register". Suffice to say that few of these records exist - who said that governments losing data is a new thing :-). The full timeline for registration law can be found on my website.
It is only since 1992 that all birth and baptism records over 150 years old have had to be kept safe, usually in County Record Offices, so many of the older registers are damaged and difficult to read, and before the 17c - 18c are often in Latin! The parish priests were, from 1598, obliged to compile records to send to their bishop, known as "Bishops Transcripts", but these are incomplete and transcription errors common.
In the south of England the ecclesiastic parishes are usually coterminous with the civil parishes, but this is much less true in the north where the former could encompass a number of townships, each of which, or a combination of them, were later to become civil parishes. If an entry cannot be found where expected, do look in adjacent parishes since there was quite a high, but local, migration.
All transcriptions, whilst welcome, cannot beat reading the original. Apart from transcription errors, much is often omitted; names of putative fathers; occupations; and especially odd comments from the vicar immediately come to mind. Finally, do not ignore the records post 1837 in England and Wales (1854, Scotland) because: registration was voluntary before 1875 in England and Wales, they can contain details omitted from the certificate, and will resolve incorrect copying of the register which may be found in the certificate. Yes, it does happen!
The best website for finding where a parish register is likely to be stored is probably the Society of Genealogists. Not many parishes have published their record details, but it is always worth trying Google. A growing collection of sites which should not be ignored is the on-line Parish Clerk which for a number of counties offers transcripts of the parish registers. Last, but not least is the IGI at Family Search.
© Ron Ferguson