British Library Direct
The BL recently introduced an excellent new service called British Library Direct - which enables users to order and download from a database of over 9 million online articles. You will need to register and when using the site do read the FAQ carefully - in particular the section on copyright payment, or you could end up paying way over the odds for an article that is only 2 or 3 pages long. The site seems to be set up to charge the copyright fee by default, although in fact you only need to pay a copyright fee if you want to make commercial use of the article. "Personal research" does not require copyright payment and it is possible to fill in an online declaration form so you do not have to pay the copyright fee. Also remember to use the "advance search" option or you may have to wade through thousands of results - a simple search for "libraries" will return over 18,000 articles.
http://direct.bl.uk/bld/Home.do