Cheers.
http://www.placesforwriters.com/journals.html
http://www.saveourshortstory.org.uk/
http://www.theedge.abelgratis.co.uk/index.htm
http://www.pulp.net/about/index.html#aboutus
There's not a whole lot of UK magazines, but your best bet is to go into a large-ish bookstore, that you can sit and read a book while drinking coffee, and pick up a copy of the UK Writer's Market -- copy addresses as needed...
EDIT: Sorry, I'm not sure if any of these are SF. I missed that in your post until now... still, you might find them useful.
[This message has been edited by HSO (edited March 23, 2005).]
http://www.ttapress.com/index.html
Site, guidelines and forum are pretty good.
They are also publishing the potentially brilliant Writers guide Success and how to avoid it. Looks good. I'm ordering my copy.
R