Re spin:
I am very much in agreement with eddie on the notion that teams should play to their strengths. There is just no point in England picking a spinner most of the time because they have 10 or 11 seamers who could do a better job most of the time.
However, IMO Croft and Giles are both Test standard bowlers on wickets like this. Giles' poor form here has muddied the waters still further. I blame the meddling around with his run - why would anyone want to do that? What was there to be gained? Giles has bowled well on the subcontinent before, with the action he was bowling with last summer.
Giles' problems this Test have most often been drifting onto the leg-stump when bowling round-the-wicket. In that his angle of run has been changed, I would say this is to blame for it.
On the rare occasion Giles managed to hit a line of off-stump or middle, he looked quite a threat. He didn't turn every ball, but he turned enough to suggest that if he kept pitching it there he'd be a threat.
If nothing else, Giles has usually been accurate. When he loses his accuracy, he loses his potency.
Gareth Batty has a good domestic record, but I haven't seen anything in his bowling here to suggest he's a Test standard bowler. Exactly the same as Dawson. Even on wickets like these.
The great need for England is to try and develop wristspinners, those who can turn the ball on any surface.
In England, as I say above, the typical surfaces at the Test grounds simply do not, for me, exonerate the inclusion of a fingerspinner. Croft and Giles are England's best spinners IMO, and both good Test bowlers on wickets typical to the subcontient or West Indies. However, their Test records in England speak for themselves.
So, if England want a spinner they are going to pick on any wickets, they need a wristspinner. The only wristspinner to play regularly for England recently has been Ian Salisbury. His inconsistency at domestic level (brilliant in 1999 and 2000, not had a good season since) means his poor Test record comes as little surprise.
The emergance of Warne, Murali (albeit he's a bit of an exception with his double-jointed wrist), Mushtaq, Kaneria and to an extent Anil Kumble has shown that the age-old stereotype that you can't bowl wristspin without dragging it down every other over (unless your name was Benaud, O'Reilly, Grimmett or Abdul Qadir) is quite wrong. Now we just need someone to have the commitment and the skill to bowl wristspin and want and be able to play for England.
The selection of fingerspinners is, for me, largely a waste of a place for England. This winter is a bit of an exception, but Giles' form this Test has been worrying considering his bowling in Lahore, Faisalabad, Karachi, Columbo and Motera. Unless he can get it back quick-sharp I don't think he should ever play for England again.