A lot of your questions might be answered from looking at topics on the
Beginners board. This topic is about searching pre-1837:
http://www.rootschat.com/forum/index.php/topic,54385.0.htmlThis one is about Civil Registration and Census (see reply no 4 on the thread):
http://www.rootschat.com/forum/index.php/topic,428062.0.htmlDifferent topics will cover Scotland and Ireland.
Unfortunately there is no one place which contains all the information you seek. Not everything is online and there comes a time when you may have to gain access to original records somehow.
If looking for people after 1837, when civil registration was introduced in England and Wales, most people tend to rely on BMD certificates, but to get all the information on them (e.g. mother's maiden name for births, informant of death, cause of death, fathers' names on marriage certificates), you have to buy the certificates and at £9.25 this would mount up. Some sites, like the new IGI FamilySearch (free!) have some extra information from marriage certificates, but it is not a substitute for the proper entry. Some sites - Ancestry is one - have images from registers held by London Metropolitan Archives available to view. This is good if you have London ancestors, not so useful if they come from elsewhere.
Is it fair to say that the 1841, 1861 and 1871 census' have abbreviated information?
Not quite sure what you mean by abbreviated information. Have a read of the topic I gave the link for about census and see if it answers your questions. If not, come back and ask or look in the
RootsChat Library for other topics which may already cover your question.
As far as subscription sites are concerned e.g. Ancestry and FindMyPast, they offer a two week free trial which would enable you to decide if you wanted to sign up for a longer subscription. Read the blurb first to make sure you know how to cancel!
Nell