Where you find isolated war graves in this country from the first World War, they are usually people who died from their wounds during recuperation. Their location only shows where they chose to 'get better'. Many town dwellers would often go to a (distant) relative in the country as the air was thought to be 'better'.
Without antibiotics, the numbers dying even after they were in full time medical care was horrific. The 12000 graves at Etaples were those who survived long enough to be evacuated from the front (pre medivac helicopters!) but did not survive their treatment at the main base general hospitals. Many others later died even after evacuation back to Blighty.
The Army Cycling Corps was a collective term for all the disparate cycling units (mostly volunteer reserves) that had been established during cycling's golden years prior to WW1. They were often separate companies within the county regiment structure. They first went overseas in 1915, but those assigned to the Western Front often found their bikes more of a hindrance than a help. Those who didn't ditch their machines were often the ones attached at Divisional level as part of their 'mounted' detachments, and deployed for communications and reconnaissance.
Because of the sort of people who were attracted to these units, they got a reputation for their cunning / bravery / resourcefulness. There was also another unit that began to get a similar reputation that also used bikes, and that was the Artist's Rifles. Many of the volunteers to that unit were 'artistic types' who if they didn't immediately volunteer for the front, were easy targets for the white feather treatment. To (over) compensate for this perception they often volunteered for more risky duties. Although all these units are now gone, some recognition of the part they played still exists. One of the TA (volunteer) SAS units still have 'The Artists' as part of their full name and have (or certainly had when I was a lad), crossed paint brushes and a bicycle wheel as their lapel badge.