i am a freelance illustrator, in late 2012 i did a series of drawings to be used in an upcoming project run by a well known charity. When i invoiced them i included a license agreement stating that the usage for the images would run for a year, as this was the understanding we had agreed to. (at the time they weren't certain if it would be a success so it was only to run for a year)
A few days ago i noticed that not only was the initial project a success but they have continued to run it over the last 2 years, scaling it up to cover the whole uk, and they have continued to use the images as the centrepiece for the project. Featuring them prominently throughout their website, advertising materials, branding etc. However i have received nothing in terms of communication and as a result im not sure how i should proceed.
I am sure this is an oversight and i would prefer to try and resolve this as amicably as possible. I would really appreciate any advice anyone can offer over what steps to take about this and wether i have a leg to stand on should they tell me to take a hike. Alternatively does anyone else think im wasting my time?
i appreciate any insight you guys can provide, or even recommendations as to who i should speak to as i feel a little bit lost. i havent contacted them directly yet as wanted to swot up before i do.
many thanks in advance and let me know if you need any more info

b