dont bother, bit like gold dust and apparently they can warp quite easily when they're galvanised. just pick up a good used one, or alternatively a brand new one for about £200-£250. cheapest we found them was £200 delivered from some landy dealer on ebay.
what you ideally want is a 300tdi defender bulkhead, because they still use the bolt on (screw on...) gearbox tunnel, which means you dont have to arse about cutting and welding aka td5 bulkhead.