Contracts can be a nightmare and complicated if you do not know what you are doing, particularly for work with a lot of specialised elements in it like building a training ground - a bit different to building a house. The spec for this would run to hundreds of pages.
If you start altering the spec after the contract has been agreed the builders rub their hands in glee as this is where they make their money. On some projects they make nothing without alterations.
In reality there will be lots of changes throughout the contract and the budget nearly always goes over as you can never think of everything. However even changes which the client may feel are minor or have no cost implications can come back to bite you big time. Any alterations or extra work needs agreeing and signing in blood.
And of course there is the other side where the client (usually an arrogant sort) doesn't see why he should bend to the hired help and tries to rip the builders off.
I have friends who make a hansom living banging heads together in precisely this situation - it is very common. So lets hope that it gets sorted, because as soon as the lawyers arrive the costs go through the roof if you loose.