How many words in a book?

I'm delighted to be able to say that I have just had an offer for my fifth Regency Lord Thurston's Challenge from Robert Hale.
This sale has been a challenge in itself as the book came in seriously over Mr Hale's required length. It appears that I had been calculating my books using the PC word count and Hale do it by 'the white space' method. This involves counting the number of words in 50 lines, then the lines on pages, taking away the number you first thought of and that's the answer!! In other words my book which I thought was 84 000 was, by this method, closer to 120 000!!
I have agreed to cut 28 pages and Mr Hale, bless him, has agreed to adjust the margins and typeface to accomadate the extra. All Hale books are no longer than 224 pages, but, it seems, the production costs are by word so it is still far more expensive to produce a book with more words.
I am about to embark on a frantic weekend removing 'the domestic trivia relating to children', of which it appears there is far too much. I have promised to send the revised ms to Hale on Monday.
I'm looking forward to seeing a copy of my first novella, Lord Rivenhall Returns, to be published in My Weekly Story collection, any day- I'll post a picture of the cover when I get it.
Best wishes
Fenella Miller