My point is that why would including a word of reference e.g. internet or broadband (so the search engine looks for webpages relating to broadband or the internet) prevent pages pertaining to upload speeds for the internet?
It doesn't "prevent" them. It just puts them further down the list of results. If you have Google's default of 10 results to a page you may not even see the ones you want.
If you type in "broadband" and "internet", the search engine doesn't look for pages "relating to" broadband or the internet, it isn't that smart. It looks for pages containing
those words. If you want to know about Virginmedia upload and download speeds, typing "Virginmedia upload download speeds" will ensure that pages containing all four of those words are ranked at the top of your results. If you put in other words you are widening the search unnecessarily.