Looking at the website of AO.com (which is as trustworthy as they come) shows that, while you can get splits of as much as 80/20 in favour of the fridge section, the best that seems to be available if you want to give priority to the freezer section is a 50/50 split.
With that split selected, a £300 maximum price invoked and their products ranked with the best reviews at the top, you get to here:
https://tinyurl.com/yy6dhbto
Scrolling down a bit, to look for a cheaper price but for a product that's still well up in the review ratings, this seems to look like a strong contender to me:
https://ao.com/product/css175wk-candy-fridge-freezer-white-66866-28.aspx
Alternatively, of course, you could buy a separate (full-size) freezer and a 'table-top' fridge.