Botched Rear Diff Repair

Just realised that previous owner has completely botched a repair to rear diff on my 90. Unbelievably it must have corroded and started to leak and he has repaired it with fibreglass and resin !!
Its not a big hole and was wondering whether you can get repair kits to weld on (if so where do you get them) or is a replacement axle the answer? Thanks

If you mean the "pan" (big dished bit) then yes you can get replacements or upgrades (look at the Gwyn Lewis site to get the idea) or you can make one yourself with the bottom of an old gas bottle

http://www.gwynlewis4x4.co.uk/product/hd-weld-on-diff-pan-diy/
Others available costing more or less including on eBay

You can also get a standard replacement if you want
http://www.paddockspares.com/lr150-diff-pan-weld-on-with-hole-for-filler-plug-rear-axle.html

Depends where it is .. maybe it's someone had a locking diff and swapped it out and just filled the hole ..

Post a pic or two to get a better idea.