@yorkshirecomrade
Here are a couple of recent threads that discuss mace swinging:
Steel Mace info
mace with s&s
I posted in both those threads, but in a nutshell I love mace (and clubbell) swinging and think it's a great complement to KB lifting.
I'm currently dealing with a severe rotator cuff tear (suffered while playing basketball, not training) that is going to require surgery, and mace swinging is something I can still do without pain. In fact, it's helped keep my shoulder functional to an extent that has surprised my doctors.
BTW, my maces are plate loadable maces from Strongergrip.com (don't know if they ship to the UK, or what kinds of maces are available over there). I have a thicker handled one (1.66") with a 42" handle, and a thinner handled one (1.33") with a 48" handle. The plate loading system on these works really well and is very secure. It's not very convenient to quickly change plates, but I don't change weights very often (I currently have both loaded to a little over 20lbs). It's more useful for adding weight over time without having to buy separate fixed weight maces. They also have a nice ball end, whereas the most commonly available maces here in the US (such as Onnit) have a straight end to the grip.
The ShoulderRok looks cool, but is the same length as my longer mace which a little too long to use indoors in my house with 8ft ceilings (I can use it, but have to be very careful not to hold it too high, and so I stick to the shorter one in the house).