Thank you gentlemen for your responses. I have also discussed the position of the slave with Frank Catt and most of the racing gt's have the slave mounted horizontally a little further aft on the gearbox, I assume a crank is then positioned where the slave originally seated to convert the now horizontal slave cylinder movement to vertical onto the arm. I can also use a rose joint as Graham said.
James, thanks for the photo, I did a search and found info on the correct Girling slave and will order one this week. I also read that the VW was too short and had virtually no spline on it!!!!. The setup photo is very useful as I can now see what geometry the arm needs to work. Your build log is and has been for a long time my build manual.
With bellhousing, box and block now in my possession I am about to dry mount the engine gearbox for the first time and sort out the position of the gearbox ears to crossmember locations. I will try Lloyd (and Paul) for an original and will discuss further with Frank possible relocation.
I have grade 8 bolts on order for the bellhousing mounting and as threatened in my build log, after 8 years of very slow parts procurement might actually be bolting some stuff together very soon..... its been a long time coming.....