I'm currently building an Avro bi plane "D" from an old Pyro 1/48 plastic kit that I found on e-Bay
The older Avros are indeed interesting aircraft.
I discovered that there is very scarce documention on these aircraft (tri and bi) and some guesswork/artistic license is in order as no two of a given version are repotedly to be exactly the same
One question I can't seem to find the answer for is how the exhaust is exited from the Green engines. Every pic of the Green engines I've found are all from the starboard side (where the intake and water jacket manifolds are located ) and I can never see any sort of exaust maifold, etc .