it is literally out of the door of the train station off the Eurostar, around the corner, through bag check, and then a one-minute walk to the entrance of the DLH.
However, if you/someone in your party has mobility problems which would make doing this an issue, you can contact the DLH before you travel, and ask them to provide you with a courtesy minibus transfer from the train station gates to the road entrance of the DLH, due to the mobility problems.