Yes, I have fixed this problem. As mentioned in the other post I opted for removing my engine to fix. There are a few posts around this site regarding methods of engine removal. I choose the "remove the gearbox first" way.
I also opted to replace my front and rear crank seals, water pump, timing belt, tensioner, idler bearing and all engine hoses while everything was apart.
Most parts are the same between the 4JB1 and 4JG2 but I found it paid to have it apart before ordering any parts.
There are two types of timing belt, squareish (trapezoidal?) and roundish tooth.
There are two types of rubber seal around the sump to crankshaft area. Most of the seal between the alloy sump and the block is done with a sealant. I used a product called Three-Bond.
There is also two types of gasket to replace the one that is currently leaking. A paper type gasket and a sheet metal one (combined with sealant). I went with the sheetmetal one.
All good so far, but I've only done about 5000ks in this since fixing.
Unfortunately my 92 4JB1 is showing signs of the same problem
This will probably become my winter project. Cant complain too much though as this vehicle has done 330,000ks without any major work