It might be worth your while to consider planning your conference in months other than February and March. Those are also very popular dates for tourists and weddings so accommodation is hard to get and consequently the rates are sometimes eye watering and not good value.
As soon as April approaches things calm down, the prices are fairer, the choices of rooms greater and the staff have more time to give you their full attention. In addition the weather is usually more settled and reliable
Food for thought! I am very happy to get a March price for you and an April price so you can see the difference.
Try it for a year and see what happens!