I'm not proud of this 'repair' to the chassis but it should do for now. Sorry about the dirt, not really got enough time to clean the thing!
On the car's right side I used a side plate of a bicycle chain, bent slightly. Bolt through the front of the chassis. Drilled though the stay and put a self tapper in from the front. The plastic nut is to cover the sharp edge.
On the left I drilled through the chassis and into the gearbox casing. I checked it clears the bevel gear first! It has already cracked the chassis around the hole (it's about 30y old) so I don't hold out much hope.
After this, the front end feels solid enough. It's going to be temporary, at next failure I'll get a new chassis.