I would think it would be enough for a return, and you should get another new screen, although there's no guarantees. If you also aren't impressed with the screen maybe a refund would be a better option. Make sure you tell them dust can get in through the gap and eventually there will be enough dust to completely ruin the picture.
How you go about returning it or asking for a refund depends on where you got it from. If it's from Dell direct you phone Dell. If it's through OcUK, you would need to phone Dell for a replacement (using work order number), or OcUK for a refund. If it's through some other retailer (or an auction site) you'll probably have to contact the retailer for either refund or replacement.
Usually the courier takes the faulty screen with swap outs.