This may be a good thing to use as well as your manual forms. You can get people to donate online via this, so no problems/headaches with collecting money etc.
http://www.justgiving.com/
You just set up your own page, and then you can link it to everywhere possible.
For got to say, this site does all of the gift aid steps for you, so you should be able to set it up so that the charity gets the tax back on the donations from private individuals.
I think it's a dead cool site!!!