Changing a bulkhead isn't as easy as you might think. They're like jigsaws. People just say they're easy to change when they're trying to sell you a defender with a shot bulkhead. I would try and fix it for now but it will have to be done at some point so when you start, make sure you won't need you're landy for a while.
I got shunted up the backside 6 months ago, long story short, the insurance comp replaced the complete rear cross-member at a caffyns garage. The chief mechanic said it was one of the hardest jobs they have encountered. I know defender mechanics who will replace a cross-member in a day but these boys took 4 weeks!