If you are interested in 11 RSF generally Ken West's book "An' it's called a Tam O' Shanter" is worth a read to get an idea of what it was like from a non-officer/non-military history perspective.
I understand you've listened to the IWM recordings of Bill Douglas 11 RSF, which deals with 59 Staffs Divn and it's disbandment and re-distribution, and the Haalderen Raid.
Bill Douglas led 16 Platoon on the Haalderen Raid and is still alive, aged 94, and in excellent health. I hope to see him in a couple of weeks. I'll ask about your grandfather. He may not remember, of course, it's only fair to warn you. It was a long time ago.