Hello!
I did this machine a long time ago, and then re-did it like five years ago :-)) Here's what it looks like:
Let me tell you, there is only one set of sprues for the Ka-25 in 1:72, so no matter if the kit is from 1983, 1993 like my first one or from 2006 like my second one, the instructions should cover it. So I'd try to contact Airfix once more and don't mention the year - maybe they would have those instructions.
The same set of sprues lets you build one of three versions of the chopper - a sub hunter (depth charges and should have a sonar, the kit doesn't have it, top secret!), a radar picket (with big bulge radar under the nose) and a rescue chopper (with a searchlight).
There are two rotors and the kit has them glued together - that's kinda bad, because they are rotating in opposing directions in real life - so that's worth re-doing IMO.
I could probably find a set of instructions if I dig deep enough in my archives, but that's a lot of work - so please let me know if all else fails :-) Good luck with your build and have a nice day
Paweł