Which lenders have you approached for the 100% loan?
The EBS only require one year's employment history and don't have a minimum income level.
It would be messy to involve your husband's parents house as even if it's transferred into his name I would presume they would have a 'right of residence' to live there which means it would be very difficult for lenders to repossess if everything went wrong.
If you could post details of your occupations, basic salaries and any additional incomes, details of any loan commitments and your ages I can work out the max. on 100% - perhaps by offering the parents house 'up front' the EBS didn't look at their own stand alone 100% criteria.....