-
Regents Park or Hyde Park
Not really enough terrain of any interest in those Victorian parks though: it's all decorative gardens and avenues with little in the way of elevation change.
Always thought the Olympic Park would make a good venue, but there's not a chance a local race would get permission to ride up those banks of wildflowers. Hopefully money talks and this'll get the go-ahead. A permanent, or semi-permanent, cross course in London would be amazing. Shame they didn't think about that during the consultation period.
Stratford is Central London nowadays.
Where could they realistically do it that's more central, anyway?
Any green space that's relatively central seems to be too manicured to get churned up by muddy Belgians.