I had this problem on my TD5, it continually got worse and worse, in the end it would take upto 5 mins to get the key to turn. I didn't like the idea of spending loads of dosh on a genuine LR barell, but also didn't want to install a non genuine one because I'd also need to have the original key near the barell for it to start as its coded. I tried to find a lock smith that could repair it, but none from round here were interested. Anyway, it all appears to be fixed now, haven't had a problem with it since I done this.....

Was leaving for work in a hurry one day, accidently slammed the disco key in the front door of the house as I left, it was really bent up quite bad, I had to get some pliers and straighten it.... its worked like a dream ever since. ha ha ha (wouldn't necessarily suggest this as a proper solution though)