Hi Cletrac:
1st Field Regiment, Royal Canadian Horse Artillery is part of the Royal Regiment of Canadian Artillery and the present day 1 RCHA is garrisoned in the Home Station of the artillery- Shilo, Manitoba.
The artillery depends absolutely on good signals. To this end it had and still has two types of signallers- artillery signallers (arty sigs) and Signallers from the Royal Canadian Corps of Signals (RCCS)/Communications and Electronic Engineering Branch (CELE) (RC Sigs).
At the Troop, Battery and Regimental level the arty sigs handle short range communications between observers and guns as well as mobile stations (CO, etc) and the regimental, battery or troop nets. Regimental net is 'owned' by the Regimental Command Post Officer (RCPO) and he has a troop of RC Sigs (complete with Capt/Lt TC and a TSM) who handle long range communications external to the regiment, radio rebroadcast (relay stations) as well the maintenance of the regiment's radio equipment.
In WWII much of the communications was still by wire and line laying was a significant responsibility for both types of signallers. Line to higher formations and operating the switchboard was usually the sole province of the RC Sigs, the arty sigs looked after inter troop and intra battery line laying. The RC Sigs would drop connections in each battery area for the arty sigs to hook into.
Based on your description, your cousin was likely an arty sig- an artilleryman qualified to operate motor vehicles as well as operate signals equipment. In WWII multiple qualifications were not as common as today, nowadays after qualifying as a Gunner an artillery soldier will usually be trained as a driver and signaller or a driver and artillery technician (the guys who do all the math and computer plotting). To get to Sergeant a gunner will usually have all three qualifications as well as extensive leadership training and more advanced gunnery training.
As to the "C", as in civi street it is simply a class of licence which describes the types of vehicles he was qualified to operate. I do not have my research library close to hand as I am on military duty in Ghana but, if memory serves me correctly, he would have been qualified to operate small vehicles (jeeps,etc), medium trucks and artilley tractors as well as small tracked vehicles like the "Bren Carrier".
The RCA Museum in Shilo has extensive records including the detailed war diaries of 1 RCHA. Your cousin's wounding will likely be mentioned in the diary entry for the day he was wounded. The diaries are fragile and the staff are small so don't ask them to photocopy a page for you. Only researchers who make reservations and come in person are able to view the records. It is simply a time and economics issue.
There are a number of MLU members who live in the vicinity of Shilo who might offer to take a look at the diairies for you... be prepared to offer up a case of beer or a bottle of Saskatchewan's finest wine!
Hope this helps,
Mike