Ok, so I found the answer myself and posting back as, although it may
seem really obvious, er, kind of took me a while to get it... and it might help someone else looking for the same answer.
{foreach from=$user_info key=k item=v}
<li>{$k}: {$v}</li>
{/foreach}
outputs:
- user_id: 2
- user_login: user_2
- company_id: 0
- firstname: Bilbo
- lastname: Baggins
- email: bilbo.baggins@middle.earth
- user_type: C
So, there I have it... {$user_info.firstname} blah blah...
<a href="https://some.custom.link/script.php?U={$user_info.user_id}">My Link To Custom Non CS-Cart Script</a>
Does the job...