checkin staff may be busy but they have been trained to look for kilo allowences on tickets and i believe the majority of tcx flights are only 15kgs ticketed anyway and if you have paid extra there will no doubt be a comment next to your name to inform the checkin staff. I havent worked on tcx but checked in many other charter flights and they all work the same. Everything is weighed, even your handluggage because all the airlines want to do is get every last £ out of your pocket.
Take it from personal experience, if the checkin agent doesnt charge for the excess Kilos they can be in trouble from their employer. Many airlines also have incentives for the agents to charge - commission, prizes, standby tkts etc
It wont really cause a hassle at the desk because you are most likely be sent away to the ticket desk to pay for your excess, depending on where you are flying from. Some agents can be extremely strict, others will let 1 or 2 go, but 3+kgs will most likely you will have to pay for, also £180 for an extra 10kgs (5 per person) you mentioned seems abit steep, again i dont have any experience with tcx but most airlines only charge about £5-£7 per kilo excess from preivous experience.
Enjoy your holiday!
