Hello my name is ***** ***** I will help you.
What is your loss please?
Yes I am just trying to understand what your loss is please?
Ok - so you havent paid this extra fee because they didnt act in accordance with your instructions?
When did you sign the agreement?
Ok - then they are potentially in breach of the Consumer Rights Act 2015 by not acting with all reasonable skill and care.
If they did not do what they were instructed to do, then they are not entitled to a fee.
Indeed you could sue them for breach of contract. So no, you dont need to pay the remaining 50%.
Can I clarify anything for you about this today please?Alex