Steering rack mount weld broken

My MK1 cabriolet has a broken weld where the steering rack mount is fitted to the bulkhead on the drivers side. Three of the weld points on the mount have pulled out of the bulkhead leaving holes where they were fitted. The other mount on passenger side is intact. Why did this happen, and what can I do about it? Is the bulkhead double skinned? Can it be repaired from inside the car or does the engine need to be removed? I've got a welder who can do the work if possible but he's never worked on a mk1 n has no idea about them. He hasn't been to see it yet but asked me to find out as much as I can beforehand as he needs to travel to me but doesn't want to unless he can actually fix the problem. Any advice greatfully appreciated. 

I'd just stitch it around the mount whilst it's all in there myself and change the steering rack bush after it's melted 

They're only spot welded on from factory, I've welded mine up fully whilst in resto. 

Mine failed its first try at MoT due to the same problem, but luckily only 1 stud. Too big a job for me, so my mechanic did it. He took the engine out to do it properly, and sorted my clutch at the same time. I replaced the rack bushes with poly as I had bought a full poly bush kit.

common problem on the mk1, a bit of plate to stiffen up the area as well as stitch welding is advisable