Well last tour England bought 17 guys and Plunkett, Joyce and Dalrymple never saw the light of day (Joyce replaced Trescothick before the tour started). So there were actually 6 fast bowlers and 3 spinners (counting Flintoff and Dalrymple), and 2 keepers named (Jones and Read). And then England played 5 bowlers in every game. So assuming that England only plays 4 bowlers this time, you can probably chop a spinner and quick off last tours squads and name an extra batsman instead. Then your 17th man might be Bresnan who would play if 5 bowlers are wanted. So your 17 would be:
2 keepers (Prior & Davies?)
7 batsmen (Strauss, Cook, Trott, Pietersen, Collingwood, Bell and Morgan)
5 pacemen (Broad, Anderson, Finn, Onions & Shahzad?)
2 spinners (Swann & ???)
1 all-rounder (Bresnan)
I don't see the need for even 2 reserve batsmen. If there are 2 injuries, you'd play the reserve keeper or Bresnan before flying someone else out. An 8th batsmen will probably be just a waste of an airfare and will just take up space in the dressing room
, even the 7th batter probably won't do much.