The last hurdles have been
The first two were fairly trivial, the last has been a bugbear.
Sending HTML email sends you back to the dark world of the late 90's web where various parts of HTML are unsupported, broken or handled differently by each client and webmail is even trickier as you have sites that munge the HTML, eating, modifying and replacing the content of the mail.
Anyway, the key solutions are to use to provide the style in a couple of ways (cid, href, in style tags) both in the HTML Header (which may get eaten) and body.
I also found some very good references but haven't the time to read through or summarise them properly so here are the links
The project itself is the company's first use of Class::DBI and it seems to be working pretty well but Openfire (our inhouse appserver/templating system) has a long way to go before it works as smoothly as TT with a handful of plugins.