Sorry, I didn't mean to panic you...
Are you planning on doing any of the work yourself? Labour is the most expensive part of any work - I spent around 200 hours building my car and many more since I finished it, on repairs and upgrades. And I'm afraid to say, the last push to IVA was the most labour-intensive, getting all the little details done (look at my blog for examples - link in the sig below).
So if you can do the work yourself, it will be MUCH cheaper and easier. If you find a pro, he'll charge, what, £50-£100 per hour? Quite rightly as it is his day job but it's expensive for you.