A single, separate, carriage charge covers the cost of all items.
We do not offer "free carriage" since we have not yet discovered such a service. Nor do we offer a "carriage paid" facility, since it is not easy to apportion costs amongst single or multiple purchases. We cannot determine a fixed carriage charge for your order until we know what you wish for. It is less convenient for you, the purchaser, to buy carriage as a separate item, but it is the only sensible way.
Calculating carriage by Royal Mail is fairly easy. Nearly all the items on this site, once they are wrapped, will need to ship as a Small Parcel. (Anything bulkier than 25mm, or about an inch.) A Second Class Small Parcel can contain up to 2000 grams of stuff, which for small tools and materials is quite a lot. (A piece of office paper weighs 5 grams.) The Post Office is designed for rapidly delivering letters, and their pricing structure quickly becomes uncompetitive above that 2kg mark, and we would recommend one of the many carriers. There is a wide choice, and there are web sites that compare their rates and services. We will gladly ship your goods by any means of your choosing, but we do not offer a "drop-off" service for anything other than through the Post Office. We quote various popular rates on our carriage page. "Other services are available."