Welcome Eve,
There were a few Pettits who received medals for the Boer War.  Including duplicated, they are:
A Pettit 	86th Company Imperial Yeomanry
A Pettit 	2nd Battalion The Buffs E K
A Pettit 	1st Battalion Port Elizabeth Town Guard
A Pettit 	Victorian Mounted Rifles
A Pettit 	3rd Battery Northamptonshire
A Pettit 	First Battalion The Border
A Pettit 	Victorian Mounted Rifles
A Pettit 	3rd Battery Northamptonshire
A E Pettit 	6th New Zealand Mounted Rifles
A E Pettit 	6th New Zealand Mounted Rifles
A E Pettit 	Rand Rifles
A E Pettit 	1st Battalion Scots Guards
Albert E Pettit 	1st Battalion Scots Guards
Alfred Pettit 	Rosmead Town Guard
C Pettit 	48th Company Imperial Yeomanry
C Pettit 	2nd Battalion Northamptonshire
C Pettit 	Coldstream Guards
C Pettit 	Coldstream Guards
D Pettit 	2nd Battalion The Buffs E K
D C Pettit Junior 	Willowmore Town Guard
D C Pettit Senior 	Willowmore Town Guard
E Pettit 	2nd Battalion Northamptonshire
E S Pettit 	Fourth New Zealand
F Pettit 	Steinacker's Horse
F Pettit 	Army Service
F Pettit 	3rd Battery Northamptonshire
F Pettit 	3rd Battery Northamptonshire
G Pettit 	3rd Battalion Grenadier Guards
G Pettit 	3rd High Light Infantry
G Pettit 	3rd Battalion Highland Light Infantry
G Pettit 	18th Hussars
G Pettit 	5th Victorian Mounted Rifles
G Pettit 	Victorian Mounted Rifles
G Pettit 	2nd Draft Volunteer Service Company 2nd Northamptonshire
G Pettit 	3rd Battalion Grenadier Guards
G Pettit 	5th Victorian Mounted Rifles
G Pettit 	Victorian Mounted Rifles
George Pettit 	5th 5th Victorian Mounted Rifles
H Pettit 	G Battery Royal Horse Artillery
H W Pettit 	Coldstream Guards
H W Pettit 	Coldstream Guards
J Pettit 	1st Battalion King's Royal Rifle Corps
J Pettit 	1st Battalion Kings Royal Rifle Corps
J Pettit 	2nd Battalion The Buffs E K
J E Pettit
J E Pettit
J J Pettit 	Coldstream Guards
M Pettit 	Steytlerville Town Guard
N H Pettit 	102nd Company Imperial Yeomanry
P A C Pettit 	2nd South Australian Mounted Rifles
R G Pettit 	4th Battalion Australian Commonwealth Horse
R J Pettit 	19th Prince of Wales's Own Hussars
R J Pettit 	19th Hussars
Robert Pettit 	2nd Battalion The Queen's
Robert Pettit 	2nd Battalion The Queens
S E Pettit 	Base Depot Imperial Yeomanry
S E Pettit 	35th/53rd Squadron 11th Battery Imperial Yeomanry
Samuel Pettit 	Rosmead Town Guard
T Pettit 	2nd Battalion Royal Irish Fusiliers
W Pettit 	11th Battalion Imperial Yeomanry
W Pettit 	4th Battalion Royal Dublin Fusiliers
W Pettit 	2nd Battery Royal Field Artillery
W Pettit 	11th Divisional Ammunition Column Prace Title-Vith Swante Divisional Ammunition Column Prace Slation Uoluheiter
W Pettit 	2nd Battery Royal Field Artillery
W Pettit 	4th Battalion Royal Dublin Fusiliers
Wm Pettit 	Steytlerville Town Guard
Y Pettit 	2nd Battalion Royal Irish Fusiliers
If you go to this page 
	angloboerwar.com/unit-information/town-guards/2610-petg
 and enter Pettit as the search term, you will see the 2 men listed, A and RJ.
There is not very much information about the PE Town Guard unfortunately.
Blayney should be easier to research as there are records for the CMR.  There is 2172 Corporal W R V Blayney who was at Wepener and received the QSA and KSA.