Buying a House

My mortgage provider halifax has valued a house i bid 67000 for at 63000, by means of a valuation survey. Various points have been highlighted that are affecting the value hence their value
of 63000. They have asked for estimates for work to put things right. They say those costs could reduce further what they will lend. Do we have to provide estimates if we intend to do some of the work
ourselves.As we think the seller will not want to go with our offer if we have stick to what halifax eventually decide.