HereForTheBeer: I prefer an actress who looks like she could physically pull off the action stuff.
I'm gonna vote for Lucy Lawless.
Lucy Lawless would have been a fantastic choice back when they made the first Tomb Raider movie, but I'm not sure fans want a 50 year old Lara Croft. Not that she doesn't still look fantastic, just no longer the right demographic for this role.
As for who could play the character now? Well there is no shortage of actresses who have the right, let's say "body type". There's bigger names like Christina Hendricks and Kate Upton but going into SyFy B-Buget movies you have the likes of Jennifer Wenger and a whole lot more, but they wouldn't necessarily be right for the part. If it's got to be someone who's British there's Gemma Arterton, Hayley Atwell (though her work with Marvel may have typecast her out of such a role), possibly Michelle Ryan and while not actually British Katherine Heigl could pull it off. A physically adept actress who is also properly proportioned for the role is a bit harder to come by, there Adrianne Palicki and Gina Carano but they are very much American. I'd almost say that Kate Beckinsale could pull it off but she's not much younger than Lucy Lawless so you have the age issue again. Not that there is anything wrong with how Kate Beckinsale looks either!