Out of interest just how steep are the climbs? I'm trying to decide whether to go for a 12-25 or a 12-27!
When I did my pb time a couple of years ago my bottom gear was 42/23, on a tt bike with a disc rear wheel.. that's tough on Ankerdine, but ok for the rest. This year I am trying a different tactic and I'm using 39 / 23 as bottom gear and my lightest spoked wheels, still on a tt bike. I plan to start out a little faster and hopefully the slightly lower gear will bail me out when I get to Ankerdine.
It's worth pointing out that the weather forecast is shocking and it's almost certainly going to be wet so rock hard tyre pressures may not be the best way forward.