To be fair the scientific community is now in line with the American notation and, IIRC, Britain officially moved over to the American 10^9 in 1974. Why we didn't have public riots is beyond me but our natural stoicism held sway and confusion still reigns here.
Most people in the UK would probably answer something along the lines of "I take a billion to be a million million but I don't know what anyone else means by a billion". In general, we're aware of both definitions and avoid the term whenever we can, clarifying when necessary with "American billion" or "a proper billion".
BTW, do we yet have any number named larger than a googleplex which is 10 to the power of a google, a google being 10^100?