Check the distance between the street lamps and you could get away with it due to a loophole.
I was stopped on edge lane Liverpool doing 45mph and he explained this about speed limit signs every 400 metres or so on lampposts, if you don't see a speed limit sign assume it is 30mph, he let me off with a warning, phew
I did end up getting banned in 97' for having a heavy foot. I have had a clean license since which is down to pure luck because it is natural to maybe go 35mph now and again
I am driving to London on Sunday, wish me luck