So, my new replacement mouse mat arrived back on 28th April from Amazon UK.
I was originally aiming for an Amazon Basics gaming mouse mat, but that became unavailable a few days before I had the money available to put the order through, so i got a Kensington Memory Foam Mouse Mat instead, which at least brand matches the Kensington Keyboard wristrest I got before I later bought my leaky old Fellowes Gel Mouse Mat (thought I got it around same time, but looking back through my Amazon orders shows otherwise)