Anthony Watson is back in contention for England's Guinness Six Nations clash with Wales on March 7 after being named in a 25-man training squad for the match.
Watson, the Bath and Lions wing, has yet to make an appearance in the Championship because of a calf problem but his presence in the group attending a three-day camp in Oxford points to his improving fitness.
Vunipola has returned to Tonga for an unspecified length of time and is a major doubt for the penultimate round of the Six Nations.
Cowan-Dickie has been limited to two superb replacement appearances in this tournament because of the premature birth of his son.
Rookie full-back George Furbank is in camp to continue his rehabilitation from the groin problem that forced him to miss last weekend's 24-12 victory over Ireland.