Insert Approval URL into HTML String

Hi - I've got a HTML template which I'm storing in a Muilt-Line Text variable (1email). I am then attempting to reference the variable in a task notification using the following syntax:

fn-Replace({TextStart}{WorkflowVariable:1email}{TextEnd},APPROVALURL,Approval URL)

(Where "Approval URL" is the approval URL reference)

The section of HTML I'm trying to replace looks like:

<a href="APPROVALURL">

<img src="http://portal/PublishingImages/Respond%20Button%20-%20Blue.png">

</a>

When the email comes through, the URL has been replaced but it is no longer in the correct spot. This is what the final HTML looks like:

<a href="&lt;span id=" NWRTEReference2?="">http://portal/WorkflowTasks/EditForm.aspx?ID=9394</span>&quot;&gt;
<img src="http://portal/PublishingImages/Respond%20Button%20-%20Blue.png">

</a>

What I am expecting is something like:

<a href="http://portal/WorkflowTasks/EditForm.aspx?ID=9394">

<img src="http://portal/PublishingImages/Respond%20Button%20-%20Blue.png">

</a>

Any ideas where I'm going wrong here? I don't understand why it's adding the extra bits of code and putting the approval URL in the wrong spot.

Thanks,

Gary