an order for sale will deal with the matter of the house but it might be an idea to instruct a divorce lawyer so that they can deal with all the financials, with 3 kids to house, you stand a good chance of getting a higher percentage from the sale to house you and the children.
Both procedures (order for sale or divorce/financial matters)will take time though and definitely over 3 months unless the pair of you can agree to settle beforehand (or he agrees to sign sale papers) so if you have to go downt his route, the application for planning permission could run in tandem to either procedure - the more money you can get fromthe sale, the more there will be for your future accommodation.
can you take a mortgage holiday to stave everything off for a while?