I will firstly give a contractual answer and then I will give you a practical answer to your question:
With the delay you describe, if the CE moves planned Completion by (roughly) one month there is an entitlement to move Completion Date by one month, and you are entitled to include prelim type costs within your CE quotation. The difference between planned Completion and Completion Date that you had generated in the last Accepted Programme is know as “terminal float” and the Contractor owns that float and it is retained in the assessments of compensation events.
Now, here is the practical answer. You had roughly two months terminal float before this compensation event with Completion Date being 16th July 2018. Whist the CE generated delay in planned Completion clearly gives you an entitlement to move Completion Date – sometimes politically this would cause more issues than it needs. If you are confident that you are very unlikely to need any terminal float and you are confident that you should still finish by June including the CE then why cause political issues buy pushing a movement in Completion Date that you don’t need? By not moving Completion Date you will still have one month’s terminal float to cover you for any unknowns that might yet occur, and either way the financial elements of being on site for an extra month you will still recover within the CE.
So it comes down to do you think you still need two months terminal float just in case, or you are confident one month is more than enough with the likely risk left on the project – particularly if moving the Completion Date politically will cause big issues to the client. I guess if you don’t know if you need the risk or not then I would follow the contract and retain the two months float whilst reminding the Client you do not intend to use it and you are “planning” to hand back the project by the “planned Completion” date not running out all the way to the “Completion Date”