DHL UK has informed us that they have started to offer a new delivery option to make sure that customers who are self-isolating or are not feeling safe to sign for a delivery can still receive deliveries at home:

Accepted at Delivery Point now available
We recognise that in light of the uncertainty regarding coronavirus that it is paramount to ensure that we have processes in place to enable consumers to continue to receive deliveries while they may be at home for a period of time.
Our delivery choices will remain in place to ensure that consumers can arrange deliveries to suit them, whether selecting a safe place for our driver to leave the parcel or arranging to collect from a local DHL Parcel UK ServicePoint. 

For consumers who want to accept deliveries at home but are self-isolating and minimising physical contact, a new delivery type description ‘Accepted at Delivery Point’ is now available.
On arrival at the delivery address our driver will knock or ring the bell and will then step away to a safe distance. If the consumer advises that they wish not to sign on the scanner, the driver will ask for their name, record ‘Accepted at Delivery Point’ and then take a photo of the premises.

If a consumer is unable to come to the door, a calling card will be left advising of alternative delivery options. A friend or family member can collect the parcel from either the local DHL Parcel UK depot or ServicePoint, they will just require the calling card, and ID for themselves and the person they are collecting on behalf of.

(Source: DHL UK Website)