LONDON (REUTERS).- The national home of British art from the 16th century to the modern age has embarked on a major revamp of its galleries starting in 2011. Tate Britain — which houses works stretching from portraits of England’s Queen Elizabeth I to modern art by Gilbert and George — said this week it would spend 45 million pounds ($70 million) on new walls, roofs, floors, improving its entrance and re-hanging its collection. Beginning next February, nine galleries in the southern and oldest part of the Tate Britain’s 19th century building will be given new walls, roofs and floors, while the domed atrium at the entrance of the gallery will be opened up, with a new spiral staircase leading down to the lower level. Under the plans, the gallery’s Millbank entrance will become the public face of Tate Britain and — for the first time since 1927 — visitors will also be granted access to the upper level of the building. Visitor