The leverage against those fixings from a heavy tool cab if the wheel hits an obstruction will soon rip them out.
Better to buy a set of flat plate mounting castors to screw to your 3x2.
Be thankful you don't have to replace these every 25k miles.
https://www.camskill.co.uk/m63b0s2193p101657/Pirelli_Tyres_Car_Pirelli_Scorpion_Verde_-_255_45_R20_105W_XL_TL_Fuel_Eff_:_C_Wet_Grip:_B_NoiseClass:_2_Noise:_72dB
My car is on it's 4th set. I did 82000 in 28 months.
If you use an...
"The longest black cable had a blue sleeve on it. I have tried using this black to the neutral and other black to the live (leaving the two red spare)"
Did you join the two reds together when you did this?
Try https://www.camskill.co.uk/
Found them the cheapest for my 255/45R20 Pirelli, fitting for £15 per tyre at my local tyre shop.
Tip: search on one device, order on a different one, as the price goes up when you go back on the same device.
Looks like it might have been made by Stuart Turner. Try calling them on 01491 572655.
They will at least advise on a suitable replacement. That one looks to have been a 3.5bar unit.