A timely sale is worth an extra £12,500 to them (and £1,700 to you).
If there is something in the survey that is cause for concern - damp / rot / ancient burial grounds etc... that you think needs a discount on the price, and they tell you to jog on, it will cost them £12,500 (and it's an opportunity cost to you of £1,700, ceteris paribus).
This gives them an incentive to agree to a discount on the sale price of up to £12,500.
Maybe worth asking off the bat why they haven't gone into the loft.
They may have already priced in the roof's condition, on the assumption that anyone buying the place would be considering going into the loft at some point.
A timely sale is worth an extra £12,500 to them (and £1,700 to you).
If there is something in the survey that is cause for concern - damp / rot / ancient burial grounds etc... that you think needs a discount on the price, and they tell you to jog on, it will cost them £12,500 (and it's an opportunity cost to you of £1,700, ceteris paribus).
This gives them an incentive to agree to a discount on the sale price of up to £12,500.