How odd, I have a battenburg cake tin, I've never used it in over 15 years. I got it from a car boot, it looks exactly like the one Lakeland sell. One day I will use it, honest. What a pointless post from me, sorry, nothing to add, as you were.
You can make one using an oblong tin and easiest way is with lakeland foil and baking parchment (think sainsburys do a version). Section the tin DIY style and it works brilliantly. If the cake rises uneavenly, just trim to shape.