Thanks for your help, I realise it's a little off-topic from indexhibit itself, but I can't find relevant advice anywhere else. I've decided to use the iframe plugin, which works better than trying to embedding the js feed, as I'm not adept enough with css to understand how to link it to a stylesheet without the whole page turning into a mess. I tried wordpress but that involved even more messing about to remove searchboxes and archives etc that I didn't want on the page.
I've modified the theme on my tumblr to make it in-keeping with the theme of my site and placed it on the 'news' page of my indexhibit site, and it works OK. All I'm looking to do now is have it flush with the menu on the left (I've tried placing the plugin script in a table but see no difference). The scrollbar is also acting oddly. On every page of my site, it has space to scroll down, despite there being nothing to scroll down to, and on the news page with the tumblr plugin it starts off the same as the others, until you scroll down, at which point another one appears inside the frame (at least in Safari it does).
I'm just trying to figure out these last two pieces of the puzzle, any help would be much appreciated.