We're considering moving up the ladder and selling our current 2 bed terrace and going for a 3 bed detached.
Going by similar houses which have sold in our street, we'd expect about 230k. The cost of our new home would be in the region of 330k.
For various reasons, including a disabled child, we would rather buy and then sell. We are relatively confident that we could sell our property relatively quickly going by what's happened on our street, and even if we didn't could easily afford a bridging loan in the interim.
Let's assume we purchase a property for 330k (additional 100k requiring to be borrowed, but have a decision in principle that we can borrow up to an extra 150k) and we agree a mortgage on that basis. However, we then subsequently sell our house for say 210k (20k less than expected) or 250k (20k more than expected).
Can the agreed mortgage be varied to take into account that we do not know how much we will actually require until we sell our house?