I went to the London Amateurs brewing meeting last Monday and yeast pitching rates were discussed. What was being put forward by the chair was that rates of thick yeast in suspension for pitching based on brewery information were suggested as ale up to 1.060 to be 1% of brewlength. So for my 23L I'd require 230mls of good thick yeast suspension. With this in mind and brewing the below I rehydrated 2 sachets of S04 in 200mls of preboiled and cooled liquor.
My brew is 1.050 and 23L and so far after 48hrs it's done this:

I usually get a drop of 10-14 on day 2, and I was so pleased 22 gravity points got consumed on the second day I thought I'd post about it

Ingredients
23L @ 66% efficiency, 90min mash @ 65°C, 90min boil, liquor = bitter
Amount Item Type % or IBU
5.00 kg Maris Otter (5.9 EBC) Grain 90.91 %
0.50 kg Caramel/Crystal Malt - 55L (120.0 EBC) Grain 9.09 %
35.00 gm Challenger [6.13 %] (90 min) Hops 25.4 IBU
15.00 gm Challenger [6.13 %] (15 min) Hops 5.0 IBU
10.00 gm Challenger [6.13 %] (10 min) Hops 2.5 IBU
5.00 gm Challenger [6.13 %] (5 min) Hops 0.6 IBU
10.00 gm Challenger [6.13 %] (0 min) Hops -
2 Pkgs SafAle English Ale (DCL Yeast #S-04) Yeast-Ale
Beer Profile
Measured Original Gravity: 1.050 SG
Est Final Gravity: 1.014 SG
Estimated Alcohol by Vol: 4.49 %
Bitterness: 33.5 IBU
Est Color: 20.1 EBC