Strangely, that's the exact situation we're in. I found this thread by googling about this apparent backlog that I keep being told that Abbey have. My fiance and I are first time buyers, getting 17.5% via the government via an organisation called Plumlife. In theory, that should be the most complicated bit, but we have been constantly delayed by Abbey - first with survey, and then the offer. We were also turned down initially, but our broker managed to talk them round!
We finally got the offer last week, and hopefully things are now moving but I'm constantly worried that they will put it back on the market. I know it would delay them to start over, but I'm sure they must be getting annoyed even though it's out of our control!