The discount for using your own cup for hot drinks is 10 pence, this is not enough of an incentive to stop people choosing disposable cups. (in Teras cafe at least)
A bigger discount or other incentive could to be offered to encourage use of re-usable cups. Perhaps a bigger discount or a loyalty card for using your own cup could be offered (free coffee every 10?).
This needs a re-think to reduce the amount of single-use cups being used - it is an easy and common option for many to just grab and go.