>if i receive a (usually HMRC related) phishing email from a .gov domain

https://www.ncsc.gov.uk/blog-post/active-cyber-defence-tackl...

>We've already started some experiments in this area with pioneering UK SME Netcraft. They're off looking for phishing hosted in the UK, webinject malware hosted in the UK and phishing anywhere in the world that targets a UK government brand. When they find it, they ask the hosting provider to take down the offending site. It's surprisingly effective and again generates data we can use. We'll definitely do more in this space.

I suspect you can forward these to scam@netcraft.com to get the upstream providers automatically notified and the site monitored until it's down.