Construction will finish in September, as plans take shape to turn it into a site of ‘international significance’.
Hillingdon Council, which is carrying out the work, aims to have an official opening in February 2018.
The centre will be home to exhibits from the Battle of Britain from both the UK and Germany. It will include a café, gift shop and lecture room.
The bunker, situated on the former RAF Uxbridge site, played a pivotal role in defending the UK during World War Two, with Winston Churchill and King George VI visiting the site during the war.
Hillingdon Council Leader Cllr Ray Puddifoot, a trustee of the Battle of Britain bunker, exclusively told Hillingdon is Here: “We want this to be something of national and international significance. It will house a variety of exhibits to do with the Battle of Britain.
“We envisage more than 7,000 visitors a year and we are particularly keen that young people see this as part of history.”
Cllr Puddifoot, Conservative, said: “It cost £6 million to build the centre and we’ve got to do some more restoration work on the bunker. It’s a big area which is open to the public at the moment, but the original communication room needs restoring and some other work needs to take place.”
The takings from the gift shop will be split between the RAF benevolent fund and the Friends of the Bunker, who are the volunteers who help run it, Cllr Puddifoot revealed.
He said: “There will be a lecture theatre down there and additional facilities which we are putting in for schools and corporate events and functions. We want entry to the bunker and visitors and education centre to be free, but we will charge some corporate visitors.
“We get a lot of visitors already to the centre but we can’t cater them.”
Former Chancellor of the Exchequer George Osborne visited the site in 2015 and gave Hillingdon Council £1million towards the bunker’s renovation.
Paul Richards, head of green spaces, sport and culture at Hillingdon Council, said: "A state-of-the-art visitors centre will be fitting for such a place of national and international significance, helping to enhance the experience for the more than 7,000 tourists who visit each year, as well as attract new visitors."
Uxbridge resident John Chamberlain, 62, of Whitehall Road, said: “It’s a good thing the site is being developed because we have to hang on to it. Hillingdon is full of heritage so it’s important we protect it.”
However, Councillor Beulah East, Labour, was critical of the council’s decision, stating the funds should have been spent on Hillingdon Hospital. Speaking at Hillingdon Council’s budget meeting, Cllr Lewis said: “Adult Social Care is shouldering a staggering £1million worth of cuts. How does this help those in dying need? This council proudly advertises the refurbishment of the RAF bunker and the building of the theatre and the new museum on the St Andrew’s site while Hillingdon Hospital continues to be not fit for purpose.”
This was a view echoed by resident Sandra Murrell, of Peerless Drive, Harefield, who said: “It’s a good thing, but I think money is tight and it could have gone to hospitals and education. It’s a nice idea, but I think it’s a lot of money.”