Having spent a lot of time in large aircraft in the Welsh valleys betwen 250 and 1000 ft, the last thing you want is a light civil aircraft in there with you! Even if you had a UHF frequency, you would hear nothing, because military aircraft don't broadcast their position, the whole purpose of low flying is to remain undetected!
Why do you want to fly down valleys at an altitude that will leave you poorly placed in the event of an engine failure, and risk encountering high energy aircraft possibily operating in formation? You must be nuts!
I recall one Saturday morning being in a stream of 15 C130s when an F111 went through our formation at 90 degrees. It ovbviously hadn't seen anything!