The ECSC is a simple contract designed for straightforward works that pose low risks to both parties. As such the pricing document is called the price list to differentiate it and its use from a bill of quantities in other contracts.
The increased quantity will be either because the works information was changed to add more, in which case the compensation event will be under clause 60.1(1), or because the original quantity in the price list was wrong, in which case the compensation event will be under clause 60.1(13). In either case it appears the compensation event will only affect the quantities of the price list. We assume it has no other effects, for example delaying planned completion or requiring other works to be carried out, or requiring you to work under different conditions. In that case the compensation event is assessed in accordance with clause 63.1.
In this simple contract, the contractor takes the risk for any price increases. We are struggling to understand your comment about delivery costs. You allowed, or should have, in your original rates the cost for delivering these materials and therefore, if the quantity increases, you will get a pro-rata increase of that allowance.