Dude who the hell is getting worked up about interest rates 10 years down the line?Oh, that sounds ok, just plan for what the interst rate on you mortgage deal might be after ten years as you might be exposed.
Over pay if possible, or invest spare money in something safe as an emergency mortgage fund once the 10yr fix is expired!
Best case scenario you won't need it so you can use it to pay for gas and electricity or childrens uni fees or whatever