if I'm understanding your question correctly.
The original Total of the Prices included 500 pile tests at £100 each so £50,000.
There has been a compensation event revising the Works Information such that there is now only 300 pile tests required.
The quotation should be based on the change in Defined Cost which in this case would be a reduction of 200 tests at £50 each + fee (either direct or subcontract depending on how the work is to be delivered). Assuming 10% fee = -£11,000 adjustment to the Prices. You will also need to consider if the CE alters planned Completion (does it save time) and any risks the contractor carries..
The original Total of the Prices included 500 pile tests at £100 each so £50,000.
There has been a compensation event revising the Works Information such that there is now only 300 pile tests required.
The quotation should be based on the change in Defined Cost which in this case would be a reduction of 200 tests at £50 each + fee (either direct or subcontract depending on how the work is to be delivered). Assuming 10% fee = -£11,000 adjustment to the Prices. You will also need to consider if the CE alters planned Completion (does it save time) and any risks the contractor carries..