Is it at all possible to add Flash to our websites? Particularly in the banners and for the tab images/buttons?
You can use custom mark-up code for your banner.. and other parts of the site. Gp.com won't (at this time) host a .swf file.
Take a look at the custom code bit of your Admin site, and use Custom Banner area. You can insert Flash by simply adding the relevant code. The .swf file will be off-site, but you can still insert it, and also insert the 'check' code, ensuring ppl can view the file.