Might be an idea to prewarn people that you will be using the service. Other wise they will just see "No Reply @..." or "MSGFRM www.freesms..." etc and may automatically delete without reading.
I know this is relatively old but, Joe if you have a mobile provider (which it sounds like you do) they usually have a web based SMS service.
O2 and Voda do as I use them both for personal and work respectively.
Usually free as long as you are contract or if you are PAYG then as long as you have topped up their minimum monthly amount.
When you spend hours typing away on here you are not actually sending a text. Maybe that is why it seems to take ages for you to text from your computer.
Thinking about it, we should not help you with this query, as no doubt you will only use the text messages as another method of trying to irritate people!!!