Wikipedia is generally an excellent website that I regularly use for my essays. My latest essay, I got a 2:1 (which is a B in American standards, I think). My main criticism was that I shouldn't use English sources and translate to Welsh, but this is because Wikipedia had all the information I wanted to include in my essay.
By the way - I too like the Wikipedia. I consult it first whenever I need info on something. Since anyone can contribute, I questioned the reliability of its accuracy at first, but since looking up many things some of which I already knew alot about to test it, I'm pretty impressed. Its a wonderful resource, and much easier than looking all over the net to find info.
Siarls, I'm sorry I hadn't noticed your post till last night! I don't seem to receive e-mail notice for all the posts. So I check the Welsh threads once in a while to see if I missed anything but clearly, I missed yours for so long.
I shall answer your question in the Advanced Welsh as you wish.