Nobody knows how many companies will be affected by the liquidation of Carillion, the true numbers will not become apparent for some time.
Most of my clients are small to medium sub contractors. Whilst they are unlikely to have contracted with Carillion directly many will have contracted with companies that look to Carillion for payment.
Most sub contract terms will include a clause that provides that should the Employer, or whoever is responsible for paying the Contractor become insolvent, the Contractor will only have to pay the sub Contractor if it receives payment for the Sub Contractors works from its Employer.
Many small Sub Contractors will never get paid for their works unless the responsibility for payment is taken up under a Collateral Warranty or the contact is novated.