The UK Package Postal Calculator is now, and will remain completely free to use. I do this because I enjoy it, find it useful myself and hope others find it useful too. Many people sell spreadsheets doing a similar thing to this site on eBay etc., and I've even been approached to package up this website and do the same thing, but that's not really the way I want to go with this. It is free now, and will remain so in the future.
Some people like to support the running costs, etc., of sites like these however, so if you would like to do so, I have set up a paypal donation account for you to use. Know that you are under absolutely no obligation to do so, and I am very happy for you to continue to use this site for nothing! Any donations are entirely voluntary.
If you would like to donate a small token of thanks however, here's a way you can do it via paypal. Please note that any donation made does not buy you anything; you get no preferential treatment, special advantage over anyone else, or the ability to demand changes to the site. You will get my sincere gratitude however. :-)
Thanks again for your support now and in the future! Enjoy!