Modification to an existing HTML/CSS Website

I have an active website that I have coded myself.
My problem is that it will not resize to fit mobile devices.

The website layout is narrow, (specifically so that it would be useable on mobile devices).
What I am looking for is for the website to reduce to fit the width of mobile screens.
I don't think I am looking for a 'responsive' solution. I don't need the website to re-arrange itself.

I believe my coding error is that I have used fixed widths (px) rather than percentages throughout the coding.
I can't face the prospect of re-coding - my brain is fried now - and I've already invested a huge amount of time in getting the coding to where it is - so I'm hoping someone can pick up the coding and polish it off

The website address is: www.lazycarrot.co.uk

The site coding is in basic HTML/CSS and I'm hoping for a predominantly CSS solution.
If you need anymore info let me know