Yes, it is possible to switch from free Royal Mail 1st Class or Weekday Courier delivery to a paid for timed courier delivery option.
Simply select an alternate option on the delivery page.
Weekday Delivery
DPD Weekday Courier by 10:30am
DPD Weekday Courier by 12:00pm
If a timed delivery option is chosen, the delivery charge will be shown on the delivery page and order summary page.