As you are separated from your husband, I would strongly suggest that you see a solicitor.(posted 8351 days ago)If the property is empty, it will have a better chance of selling. Most buyers aren't happy to purchase a house when there are sitting tenants.
If you can afford to, freshen the house up with a lick of paint, do odd jobs that require little effort and little costs - those jobs we know we need to do but never get round to! Those little things will all go to help a sale. Also have a word with your local estate agent, see what else you can do to encourage buyers. It may be that you're best changing agents. Make sure that you get one thats does a no sale no fee.
If the house has any amount of equity in it,then it may well be worth investing a little in it to get it sold.
To surrender the property, or to have it repossessed, is not a choice you want to make without giving it great thought. Read through the website for advice and information on what other people have done. but I suggest that you see a new estate agent and a solicitor first.