This stretch of towpath to the west of Redmile (and heading towards Barkestone and then Plungar) has been surfaced with compacted stones and is therefore a bit better drained and generally less muddy than the purely grassed section to the east of Redmile. From GZ you should be able to see a WW2 pillbox (a local source tells me it is a type FW 3/22 but I cannot vouch for that) which is across the canal. The pillbox is on private land with no footpath that I can see on the map so this is possibly the closest view that you will get).
There is also plenty of wildlife to see on this stretch of the canal (as indeed there is along it's entire length).
Whilst this stretch of the canal should be ok for bicycles and all terrain buggies, it is probably not wheelchair accesible, due to the steep slope / steps at the redmile access point onto the towpath and the narrowness of the towpath under the redmile road bridge.
You will not need to go close to the water's edge to get this cache. This is a generally safe environment although clearly the usual caveats regarding children safe when near water should be adhered to.
I have found some picture of the pillbox posted here Pillbox
Congratulations to Northking and PlasmaWave on their joint First To Find