I read a reference to an old post that stated that there was a drain valve at the bottom of the small fuel sump tank. I looked and found a rubber grommet . which I removed and used a 19mm socket to turn the nut CCW and sure enough, the residual fuel drained. Here are photos.

 

Well found.

That is a SPECIAL Jag, the hole on the floor actually lines up with the drain spigot, RARE.

 

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In order to get the wrench socket on the drain valve I had to slightly reposition the hole. I used a 1 1/8" hole saw with a 1/4" pilot bit. Inserting the bit in the drain tube and with a drill moved the hole about 1/8" with the hole saw cutting just one side of the opening.
The grommet fit after, but will need some silicone on one side to completely seal.

 

My surge tank drain was completely seized solid; couldn't even undo it with that little tank out of the car!

I found an alternative fairly easy way to drain the tank - Go take off the fuel hose in the engine bay where it connects to the first fuel pressure regulator & place in container on engine. Then pull the fuel pump relay out(in the boot, right hand size), bridge the two switched pins together in the socket with loop of wire to run the pump. Drain tank directly into a container, no mess.