No different to Farnboro's constant "clearances" through their overhead at 2400' and "transit" approved while outside their ATZ. Cambridge is pretty well out there on it's own and there isn't a really good reason to overfly it, but, if that's your want, so-be it your in class G and have every right to do so. Making the calls you have is more than sufficient to assess the traffic, so why do these airfields have to assert their non existent "authority" all the time. When I was working the old adages of "custom & practice" soon became accepted as the norm and then became "the Rule" this is what they try to instill into everyone.
Hopefully this is the start of Cambridge and others wanting their much needed Class D airspace.
You do say some strange things don't you?