An update. I have now fitted the new slave cylinder mount, bottom studs need to be removed as there is no clearance to fit it over them, thankfully with double nuts locked these removed easily.
The new cylinder is made of steel, but has identical mount and piston bore and diameter, but it has a 3mm shorter stroke, which I don't believe will be a problem. All fitted ok, and swapped over the pushrod assembly from the old to the new. Bled system,( or so I thought,) and checked operation. Car driven in and out of the garage only. I had bit of play in the pedal before it took up, air still in the system, attempted to bleed further but school boy error, had the car up on front ramps only! Levelled up but still get a fair amount of air, I will leave it overnight to settle and try again in the next day or so. I do believe this cylinder will be fine. Watch this space lol.