If I go to a solicitor now though it'll wreck Xmas and I really don't have any money to shell on their fees
What can I say? The statement you've made above doesn't inspire confidence that you are 'determined' to change your circumstances, and it seems to me you may be looking for the type of sympathy and support type that tells you this situation is not of your making and you shouldn't hold yourself in any way responsible for the less than harmonious environment your older dc were raised in and your youngest continues to endure.
I am also a 'rock' to many in my professional life and I don't "burden" colleagues or clients with my problems because I do not cross the boundary I've set between my professional and personal lives therefore, other than taking a minimal amount of time off as annual leave should you have to attend solicitors/court etc, I see no reason why your marital problems/issues should adversely impact on your work and more especially as you have clearly been able to compartmentalise them to date.
I've shielded the kids a lot. It could've been much much worse but I don't think you'll understand I understand only too well that it's not possible to 'shield' dc to an extent where they are not harmed by living in an environment where they see/hear one of their parents physically/verbally abusing the other on a regular, if not daily, basis.
I also understand that abuse can be insidious; it can break the spirit and grind the recipient down to a point where they feel powerless to bring about any change in what becomes an 'existence' as opposed to a 'life'.
In addition, fear of retribution has kept many trapped in abusive relationships until death has ended their suffering and, sadly, some have met their deaths at the hands of their abusers because they felt unable to leave.
Economic dependence plays a part in many abusive relationships but you are not financially dependent on your h, nor are you restricted to your home in the way in which many other victims of abuse are constrained from interacting with the world around them.
Of course it's "all a lot more complicated" than what you've posted here; it always is because, other than in the obiturary columns, no life can or should be reduced to a few short paragraphs, but there is no unhappy marriage so "complicated" that it cannot be ended by the divorce courts.
The questions I've asked in my earlier post (above) are no more than will be asked by any solicitor you consult and were intended to enable me to help you gain the most successful outcome which, in your case, would be for your h to leave the marital home thus alleviating you of the need to find alternative accomodation and reducing the possibility of your youngest dd wishing to remain with her df, which may require you to pay child maintenance to him while struggling to repay debts that may have been accrued due to his idleness.
Your post reminds me of others on this board from women who have, in effect, spent half their lives tolerating and appeasing their abusers but who balk at taking the first steps to freedom because they lack the courage to do so.
If you would only realise that you have shown immense courage in building and holding down a career while living with intolerable abuse from a selfish twunt who treats you with the utmost contempt, nothing anyone says here or elsewhere would be able to dissuade you from getting out from under at the earliest opportunity.
Fwiw Women's Aid provide accomodation for women who wish to leave abusive relationships but, as you are unlikely to be placed in a refuge anywhere near your home, going down this road may mean that you would need to take an extended leave of absence if you are unable to commute to work. However, I would suggest you make contact with your local branch to ask for recommendations for solicitors who are experienced in dv cases and who offer a free initial consulation. www.womensaid.uk
Alternatively, you could ask friends/colleagues for recommendations using the guise of doing so on behalf of 'a friend', or post on the Legal board for for details of solicitors who specialise in divorce and family law in your general area, central/south/east/north/west London, Surrey, Northumbria, etc etc.
Be prepared to be especially tearful as the loss of your df is still raw. Grief can overwhelm us with sorrow, but it can also give us moments of great clarity and you may have experienced an 'epiphany moment' where you were able to see that there is no compelling reason why you should continue to live as you have been doing and, indeed, that life is far too short for you to do so.
Make your mantra 'i CAN and i WILL' and take heart from posts such as that from TopOfTheCliff who has proved it is 'do-able'. Many here will hold your hand as you go through the various proceedings but, as is so often the way, only you can do it..