What is the absolute minimum track spacing that is obtainable with home pcb etching i need round about 0.1 to 0.2 mm.....

 

.1mm is typically the min for professional etching processes.
Using a pre-sensitized clad/UV process it might work...
Toner transfer method is out of the question.

 

I can get about 0.2 mm on a bathtub homebrew effort. That's with an inkjet photopositive onto acetate, print side towards the PCB, pre-sensitised board (don't bother trying to make your own with aerosols), exposed with a small tanning lamp and a bit of greenhouse glass, developed with sodium hydroxide and etched in ferric chloride in a paint roller tray. The devil is in the detail, so refine your process to suit your setup. That said, I prefer a minimum 0.3 mm track width and clearance for a home board, and I doubt I'd get consistently good results at 0.1 mm. Smaller geometries I prefer to farm out to PCB houses, preferably continuity tested if it's that tight.

 

While it won't meet your needs directly, a good site to bookmark is Tom Gotee's PC instructions using Laser printer toner...

http://www.fullnet.com/~tomg/gooteepc.htm

There is quite a bit of stuff in the beginning of the website, but it gets down to business in the bottom 2/3.