Pants on Fire Press have contacted me to tell me they are currently accepting unsolicited manuscripts for picture, middle grade (equivalent to the 8-12 age readership in the UK) and young adult books. Based in the US, they are a small independent publisher keen to expand and explore new areas of technology as well as traditional printing.
Submission details can be found here and they prefer an initial query letter sent as an email.
Lou Treleaven 
Dear Lou
Thanks ever so much for the info on pants on fire. Wish me luck I have just sent off an enquiry letter.
Thanks again
Rhys Rithenmere
That was quick, Rhys! Good luck!
Thanks for the “Pants on fire” lead.
Fyi Pants editor email is down
Did you try this address: submission AT pantsonfirepress DOT com?
No. I used the @ sign and the period for the dot. I’ll try again thanks
Well, Lou, I just tried the new address with no @ or period and it wouldn’t even send. Not a proper address. What do you suggest next?
No, you need the @ sign and the dot! Sorry, it’s just that some sites prefer to type their email addresses out literally in order to minimise spam. I wonder whether they have omitted an s at the end of submission by mistake?
I have confirmed with the publishers that the email address is definitely submission@pantsonfirepress.com.