Who is the house builder?
Personally, I cannot see why anyone would agree to having any advertisement on their home, irrespective of how much they were paid.
The fact that they have not even offered you anything to do this shows just who you are dealing with.
My advice would be to cancel the reservation unless the advert requirement is removed.
In fact I would go further and suggest you walk away from this builder.
As this is an unfair trading contract term, you should get a full refund of your reservation fee.
If the builder tries to refuse, tell them you want a deadlock letter so you can use the Consumer Code for Home Builders Arbitration Scheme.
(If you end up making a claim, you should also claim for £250 for inconvenience as well if you do this as well as the £120 application fee!)
Right up to Exchange of Contracts, either party can withdraw from sale/purchase.
I doubt anyone would buy that home on the basis of a builders advertisement all over it.
If you do decide to buy, tell the builder that unless your home is finished to very high quality, you will put your own banner (available from Vistaprint) on the balcony warning potential buyers to go elsewhere!
