So, if you are interested in mathematics teaching in general (and in the UK in particular), you should definitely take a look! Hopefully, the archive will continue growing, and I wish other journals would follow up and do the same thing (preferably with a large collection of freely available back issues)!
The ATM journal Mathematics Teaching has a very nice (and growing) archive where several back issues are available in PDF format. Some articles/issues are only available to ATM members, while others (quite a few, actually!) are available to all, for free. In the archive, you can even take a closer look at the first issue (ever) of the journal, from 1955.