WHSmiths people were helpful but DHL has two services and the one I wanted wasn’t available at WHSmiths. Make sure you check first
From DHL Express Service Point (WHSmith Teddington)
DHL’s fast and secure worldwide delivery service available at 1,200 locations nationwide. UK & international delivery. No account required, simple pricing based on 7 free DHL envelope and box sizes. Free tracking and signature on delivery (where available).