If the buyer or seller fails to abide by the conditions or terms of the contract they are said to be in breach of contract. E. g. , if they fail to complete on the stipulated date. Where this happens the aggrieved party may sue for breach of contract and claim damages. If the buyer fails to complete they immediately forfeit the 10% deposit they paid on exchange of contracts and in addition to that the seller may still sue for breach of contract.
The remedies available for breach of contract will depend on whether there has been a breach of a 'condition' in the contract (then the aggrieved party can terminate the contract and claim damages) or a 'warranty' (in which case, the aggrieved party can only claim damages).
A term of the contract will be viewed as a condition if it is a major or fundamental term. If it is something minor it will be treated as a warranty.