Well, I had a bit of disaster in my keg. I'd made myself up a batch of Wassa's Honey Porter, but the hops that I used were kinda brown, not the bright green that they start off as. I thought that it wouldn't be too important, despite all the stuff I've read about oxidation etc. I was wrong. Once it was in the keg and had carbonated and cleared, I tasted it and was really disappointed, sweet, and absolutely no hop flavour or aroma. After a few pints, I resolved to do something about it.
Having read this thread, I opened my beautiful 450g bag of Cascade pellets from Ross, and put about 8g of them into a normal
spring loaded tea strainer (boiled it first to sterilise, then added the hops). Dropped the whole thing into the keg, and after a couple of days, the beer is completely revitalised, with that beautiful strident cascade flavour that goes so well with this kit.
So, a successful dry-hop-in-the-keg story.