Eeenie meenie... what next?

People are always asking me 'where do you get your ideas from' and I have to explain that I never have any problem with ideas, more that I never have enough to time to write as much as I would like. This is a problem which is exercising me right now.
I have finished my non fiction book about Gigha and I'm still waiting for publication date, which has been postponed for a week or two. But the launch of what has turned out to be a rather nice (ie nicely produced!) illustrated hardback is scheduled for 22nd November, so I'm assuming it will be in the bookshops by then.
Which in theory, means that I should already be deep into a new book. What contributors to various writers' message boards call the 'WIP' or work in progress.
And I am. I really am.
I have an idea for a brand new novel. I have a working title for it (The Fifth Mary). My agent thinks that it is a good commercial idea, with interesting characters and a strong plot. I have done lots of research. Although not a historical novel, there is a historical mystery, related to Mary Queen of Scots, at the heart of it. I have written a long and detailed synopsis (30 pages or more) and already have a few chapters under my belt.
So what's the problem?
Well the problem is my last unpublished novel, which is still tapping at the window of my consciousness and wailing 'Let me in! Let me in!'
I finished what I thought was the final revised draft of it (then called Darragh Martin) about a year ago, but Polygon/Birlinn who published The Curiosity Cabinet and ARE publishing God's Islanders within the next few weeks, didn't even want to look at it, on the grounds that it didn't fit their current list.
So my agent sent it out to other publishers, but the reception was lukewarm to say the least, so I did what all writers do in this situation - filed it away in the bottom drawer, and pressed on with something else, in this case a new play, which was subsequently produced in Glasgow, and a new non fiction book, my history of the people of the island of Gigha, which is about to be published in hardback and which has taken just about all my time and energy for the past year.
About six months ago, I took Darragh out of his drawer, scanned through the chapters, looked at some of the feedback from publishers, and realised that for the most part, they were right. The structure was too complex, and - perhaps more important - there was a gaping hole at the centre of the novel, and at the heart of one of the main characters. I didn't do anything about it at the time, since I was wrestling with God's Islanders, but made a few notes, and closed the drawer.
Not long afterwards, I came across a couple of references to the corncrake, in poetry, and started doodling the name on the old manuscript. It seemed peculiarly evocative of one of the characters, who comes and goes like that elusive bird.
Then the dreams began.
It is, I have to say, rather like being haunted.
The characters knock at the window of your subconscious, refusing to be ignored.
They lurk at the back of your mind, popping up at inopportune moments.
This is what I do, they say. This is where you went wrong. This is the way I am. This is the way I have to be. And what are you going to do about it? And what about this scene, and this possibility, and why did you never explore that bit of me?
It is almost sinister in its intensity.
Now, whenever I try to knuckle down to the new 'work in progress' the old one intervenes, muscling in, demanding attention.
So a couple of weeks ago, I got it out again and started revising the synopsis and suddenly it all slotted into place, and I thought 'No wonder nobody would buy it, because this, this and this was wrong with it, and now I can see, and now I need to do this, this and this to put it right.'
Which is what I am about to do.
Darragh Martin has become The Corncrake. Instead of being told from several different and unnecessarily complicated perspectives, it is going to be told in the third person as a straightforward (and rather different) story, spanning the years from the 1950s to the present day.
I will try to write the WIP while I am doing it, but I make myself no promises. And in any case, I may be on a hiding to nothing, because even when I have finished it, who will take a second look at a rejected novel?
Better better better says my head to forge on with the new.
But all the same as Ceit and Darragh, but especially Ceit, lovely, magical Ceit, who got so short changed in the last version, pace through my mind, demanding to be heard, there's nothing I can do but write the novel as I now know it was meant to be.
More in due course.