From BBC Catchphrase:

In February 2002, Barry wrote to us to ask: "Did you know that J.R.R. Tolkien based his Elvish languages on Welsh and Finnish? Neither did I until I found the item below in "The Spectator"...

www.spectator.co.uk/article.php3?table=old§ion=current&issue=2002 -02-02&id=1420&searchText=welsh
{note: note sure 'bout that link}

Following on from that message, Pavel Iosad wrote from Moscow in Russia to say: "Thanks for including the info on Tolkien's inspiration in the newsletter. I am appreciating this as an amateur Tolkien linguist very much, since drawing attention to our little community can do nothing but good (a little confession: I actually started learning Welsh because I was so impressed with the language based on it :-)). ...you could refer the readers of the Catchphrase newsletter to Tolkien's illuminating essay "English and Welsh", which is as good a starter point in Welsh philology as can be."

read the rest here ~~
http://www.bbc.co.uk/wales/catchphrase/catchphrase/ref-tolkien.shtml