Hi yes, i created some other wallets and sent £2 to them from the offline one, same problem. I've done this method before and it has never been a problem. I can only think it must be a glitch.
I think you may have downloaded a fake copy of bitaddress. Can you check the addresses you funded on a block explorer? Are the coins still there, or have they been moved?
Try opening the offline version of bitaddress you have downloaded and paste in one of your private keys. Make note of the compressed and uncompressed addresses. Do they match the addresses you have funded?
Now go to the bitaddress github (
https://github.com/pointbiz/bitaddress.org), download, and run offline. Paste in the private key. Do the addresses generated match the ones you just generate in the previous step?