Here is a photo of the studs.
The middle one is in good shape and obviously came out without a hitch.
The left one is corroded about 5mm below the head but this one didn't snap..i think all the others were like this but did snap.
So I now realise I can't really carry on removing the gearbox as I need to support the engine with that removed and whatever I use will be in the way for removing the studs.
I could support the engine take the box out, fit new RMS/IMS and clutch, refit box and do the studs but if I can't get them out in the car I am going to have to take the engine out and remove the heads meaning I will most likely have to take the gearbox off again..the joys