Gotta be honest, 90% of what I send now is tracked.
Check the thickness if they have a "large letter" size. It can make a serious saving on post costs ! The UPU (Universal Postal Union, an international association of various countries' post offices) has set a 3cm standard, but Royal Mail makes it 2.5cm. It enables them to make extra money on international cross-charges for items from 2.5-3m thick.....