The documents only need to be carried within the UK if the flight is for the purposes of public transport, and even then can be left at the airfield if the flight is to start at terminate at the same place.
Insurance documents are not mentioned because, as always seems surprising, there is presently no legal obligation to insure the aircraft. Of course it is sensible to carry the insurance certificate along with the other stuff and many airfields stipulate that visiting aircraft must be able to prove that they are insured up to a certain level.
I don't know of a web source for the interception procedures. When going overseas I stick a copy torn off the cover of an old VFR guide onto my pad.