Saw this one pop up and it's not far from home so dashed out to see if I could get a FTF. I never knew the bunker was there so thanks for bringing me here - very interesting - presumably wartime?
Found the cache easily as it's visible from the path (if you know where to look). Tried to hide as best I could but would suggest you move it slightly to avoid the cache getting muggled in the future as that would be a shame (I'll email you).
Great to see geocaching is being talked about in lessons at school - it's a great hobby that our 7 year old thoroughly enjoys. He learns a lot from it and I'm sure others will too .