All sigs free. The only people I've ever seen charge in 20+ UK cons are Neal Adams (£20), Humberto Ramos (£3 or £10 for ASM 1), Mike Zeck (not sure how much he was) and Alex Sinclair/Scott Williams (free but only if you bought something from them). Those last four were all from last weeks LSCC.
As for sketches, Sakai was £55 for a quickie sketch or £140 for a more finished piece. He also had some pre done sketches in his folder that ranged from £100 up to £300. He was doing quick 1 minute sketches for free in each book he signed. My sketchcard size piece was £25.
Other prices were:
Lew Stringer - Beaker £5
Gary Whitlock - Piggy £5
Jesus Merino - Gen - free but I bought a print from him (He was charging £60 headshot, £80 bust, £100 Full fig)
Doug Wheatley - Jei - free but I bought a print (not sure what he was charging for sketches otherwise)
The only other artists were Jim Balent who was doing free sketches for anyone who bought some stuff from him and Jorge Molina who was £100 headshot, £150 bust, £300 full fig.
This is a not-bad source of prices.