The answer is yes (I have discovered). THE KL site is, however, misleading.

Always make a reservation for your special baggage at least 48 hours before departure, and ensure your reservation is confirmed.

In fact, if you rang 48 hours before departure you could be disappointed. I fly next week and rang today. I have to ring after 48hours for confirmation that the request has been approved. Approval is not guaranteed, but as I am flying in C and as I am a GE, I was given a strong indication that it is likely.

What I also had not realised (and what is not stated on the site, that I can see) is that when you ring to book you need to have the dimensions and weight of your golf bag. I can see some sense in ringing ahead now.

I have a sneaky suspicion that someone on a low-cost fare would find that if they rang 48 hours before the flight, then checked for approval on the day, they would find there is no room at the inn for their golf bag. They could, of course, seek approval much earlier, but I think the KL website is not helpful in encouraging this.

I have confirmation that I can take four hold bags, golf bag (including clubs and balls) plus cabin bag.

Thanks to all those who replied. I hope this thread may help others thinking of taking a golf bag on KL.