In reply to saulward:
> I went into a big outdoor retailer to buy a rope for climbing centre use and the guy sold me a Edelrid Shikra 50m,
If you made it clear you wanted it for indoor use and then some sales guy sold you a half rope, then the guy was being a dick. He should have known better, and if he didn't he should have checked with someone who did. I would take it straight back and, particularly if you're a beginner relying on their advice, I think you have a good case for being quite upset about this.
Learn the difference between rope types so you have a better idea of what you should get next time. Shop assistants should be there to help, but as you have found out here - you can't trust them all.