I really don't understand your issue? As a civil engineer you will know that fixed fee pricing is common for both consultancy and construction contracts. You were quoted 360 for a whole days work. The fact it took half a day is mainly a bonus for the contractor, not you. You will also know that the way to make money on fixed fee is to do the work as quickly and efficiently as possible. You really can't be mad that someone else also knows this.
You accepted the cost when you signed the contract, it's not opportunism. If it wasn't a fixed fee then go back over the contract and argue it contractually... if you can. I would imagine the 360 was quoted as a minimum charge though.
As a chartered engineer I seriously doubt your charge out rate is less than 80 an hour? And I assume your company pays your subs? Gives you holiday, pension and other benefits? An office to work in? Indemnity insurance? Where do you think the money comes from for that?
You accepted the cost when you signed the contract, it's not opportunism. If it wasn't a fixed fee then go back over the contract and argue it contractually... if you can. I would imagine the 360 was quoted as a minimum charge though.
As a chartered engineer I seriously doubt your charge out rate is less than 80 an hour? And I assume your company pays your subs? Gives you holiday, pension and other benefits? An office to work in? Indemnity insurance? Where do you think the money comes from for that?