www.cleaningdoctor.net/bournemouth
This is interesting as in; does it mean that I may be getting a different result than others by putting in carpet cleaners durham? 
yes if you have personalised seach on for google (go to your google account and check setting page) or if not logged in if you have cookies enabled then you'll probably be getting custom search results.
your history should not effect your restuls as google will not be able to know your history for obvious reasons, however i may not know if say firefox has done a deal with google and they tell them, though i highly doubt it.
mary: backlinks are simply like recommendations in real life. say i need a builder. i ask you if you know anyone, you suggest building company xyz. xyz go higher on my choice list. if i look at xyz and they turn out to be dodgy, my opinion of you will be lowered so you'll go lower on my choice list. also you recommendation will only count if you are related in this field, e.g. you're a decorator so would have enough experience to give a good recommendation, if you're a doctor recommending a builder then my opinion of your recommendation wont be so high as you most likely wouldn't know a good from a bad.
that's how backlinks work