Edited: 18/3/2018 with screenshots and to recognise an update.
Some genius at work pointed out that the contact forms on the works web site weren't validating properly.
Whoops, my bad.
So I changed the email and telephone inputs to their proper HTML5 types, but there was the postcode box that the spammers where filling in with crap, so I wrote this little plugin for Contact Form 7 that adds postcode validation.
Once installed, it adds the Postcode option to the form builder:
Add the usual id, class and required options.
It's free to use and abuse as you feel necessary, just a link back to the original would be nice.
Congrats to MrJoshFisher for adding placeholder support, I LOL'd and LOL'd when that came up 🙂