How best to release 3 baby wild rabbits back into wild ?

(England UK)

Hello -

I have 3 baby wild rabbits that I've looked after since they were 3 weeks old three weeks ago. They are now weaned and each weigh just under 400g. They have been living outside in a safe cage standing on grass. There were four rabbits until today when we found one lying on the grass dead; I have no idea what it died of.

Nearby there is a large wood and a field and I think other groups of rabbits are living there. The wood is where we found these ones.

How should I put these three into the field safely ? Will they be accepted by the others? Should I make a sort of burrow nearby the others? How much longer should I keep them in the cage ?

In the photo I'm standing at the entrance to the field about 70m from the garden where they are currently living.

please help if you have advice !