You are nicer than I would have been, he would be at the bus stop with a matching set of bin bags if he was mine. Try & get some sleep & tomorrow ring around solicitors, don't immediately go for the cheapest one, paying a little more can save you money in the long run. Your kids are grown up so you won't have to go through the family courts ordeal, just the separation of belongings & finance. Can you take a couple of days sick leave to give yourself time to come to terms with the news? When he goes to work tomorrow gather all your evidence ready for the solicitor, marriage certificate, bank & pension statements, payslips etc, make sure he doesn't take the car if it is in your name, you can always hide the spare keys to make sure. If you have a joint bank account check he hasn't cleared the account & get yourself an account in your sole name, get your salary paid into it, you can also transfer half the balance in the joint account.
Do some detective work, look for receipts or unexpected payments from the joint account, has he got a new credit card in his own name? Go through coat pockets & bedside drawers as well. If you have credit cards where you are the first named on the account but he has a second card, get his card cancelled.
Under the new divorce laws it should generally take you 6 months from the application to the final order & decree absolute, if you are on a low income you can get help with the divorce application fee which is £612 & then there is a further fee for the financial consent order. Check if you are able to claim Universal Credit once you are on your own which may mean you get help with your rent, council tax, free prescriptions, dental care etc.
Look at the 6 months the divorce will take as time to adjust to your new life, by the end of the summer hopefully it will all be over & you can move forwards, you have nothing to blame yourself for, this is all on him.