I've the following code, I would like to modify it to change the placement and display of axes, as outlined below.

Chart generation (Playground)

import SwiftUI
import Charts
import PlaygroundSupport

struct BarChartExample: View {
    let data = [
        ("A", "Z", 5),
        ("A", "Z", 5),
        ("B", "Z", 10),
        ("C", "Y", 7),
        ("D", "Y", 3),
        ("E", "Y", 12),
        ("B", "Y", 10),
        ("C", "X", 7),
        ("D", "X", 3),
        ("E", "X", 12)
    ]

    var body: some View {
        Chart {
            ForEach(data, id: \.0) { item in
                BarMark(
                    x: .value("Category", item.0),
                    y: .value("Value", item.2),
                    stacking: .standard
                )
                .foregroundStyle(by: .value("Category", item.1))
            }
        }
        .chartXAxis {
            AxisMarks {
                AxisTick(centered: true, length: 10, 
                         stroke: StrokeStyle(lineWidth: 2))
                AxisValueLabel()
            }
        }
        .frame(width: 300, height: 200)
        .padding()
    }
}

// Present the view in the Live View window
PlaygroundPage.current.setLiveView(BarChartExample())

Results

Desired outcome

• I would like to move y-axis to left hand side
  • Including scales
• Modify colour of axes and show them as white thick lines (consistently with the provided visual)

I've tried playing with AxisGridLine and AxisTick but I can't arrive at the desired result.

try using

.chartYAxis {
    AxisMarks(position: .leading) 
}

EDIT-1:

Here is a possible approach to display the X and Y axis lines as shown in your picture, using chartPlotStyle with overlay. You will have to adjust the colors.

struct ContentView: View {
    var body: some View {
        BarChartExample()
    }
}

struct BarChartExample: View {
    let data = [
        ("A", "Z", 5),
        ("A", "Z", 5),
        ("B", "Z", 10),
        ("C", "Y", 7),
        ("D", "Y", 3),
        ("E", "Y", 12),
        ("B", "Y", 10),
        ("C", "X", 7),
        ("D", "X", 3),
        ("E", "X", 12)
    ]

    var body: some View {
        Chart {
            ForEach(data, id: \.0) { item in
                BarMark(
                    x: .value("Category", item.0),
                    y: .value("Value", item.2),
                    stacking: .standard
                )
                .foregroundStyle(by: .value("Category", item.1))
            }
        }
        
        // the axis lines
        .chartPlotStyle { plotArea in
            plotArea
                .overlay(alignment: .bottom) {
                    Rectangle()
                        .fill(.red)
                        .frame(height: 8)
                }
                .overlay(alignment: .leading) {
                    Rectangle()
                        .fill(.red)
                        .frame(width: 8)
                }
        }

        .chartYAxis {
            AxisMarks(position: .leading)
        }

        .padding()
    }
}