Hi Chris Thomas,
I have been running PC Tools Firewall Plus now for around three weeks. It uses minimal resources and is very user-friendly. Personally, I would recommend it!
The choice of a firewall is a personal preference. As you know, protection against hackers and other nasties involves a layered approach. That is, install a good anti-virus programme (my choice is Avast Pro), use a well-respected anti-malware programme (my choice is Malwarebytes Anti-Malware), keep all of the aforementioned as well as Window$ up to date and most importantly stay away from the porn! :-)
Hope that helps!
Avastfan1