historyenne, I had a similar problem. My samples were a bit old, so I mentioned it in my initial contact email. But, it was fine.
Anyway, you are smart, so I am sure your samples are great. Even if they are old, and even if you feel you write better now!
I think it is a fairly common problem, as a lot of people take a few years to go back between programs.
Could you perhaps, in addition to your former work, include something you have mocked up that reflects your current skills? I don't know if that is done here but I have seen it done in the USA!
I sat on the PhD reading committee for the masters programmes at The Cooper Union and a few students returning to school after a long absence did do exactly that! They provided former work, and a mock up, and clearly stated which was which in the cover letter and in the paper heading.
Just a suggestion/idea. Something to consider, and maybe look into...
xoxoxxo