We're now back from our travels - which we thoroughly enjoyed incidentally. I can't say when work on the car will recommence as I have to find gainful employment first. However, I have had a look at the chassis and can confirm that the oil and stretch wrap method appears to have done a great job of keeping the rot at bay - it pretty much looks like it did when we put it away. Moral of the story: if you too need to lay-up an unfinished chassis or any other raw steel part, it's worth investing a bit of time to store it properly. I'm just not willing to contemplate the joys of the degreasing process at this stage.