Looking at Mr Malty suggests that I should pitch the whole 2l. I had intended to use 1l and keep 1l in the fridge to split in the future.

I made the starter in a sterilised 2l milk bottle and there is a good thick layer of yeast at the bottom (~ 1cm). I guess I could pitch the lot and could wash and recover the yeast after fermenting.
I intend to pitch tonight and would be grateful for ideas on the best way forward.
Thanks
Jon