Some stouts are most definitely intended to taste of chocolate. e.g.
https://www.beeradvocate.com/beer/profile/664/73/
(That's got quite a few fans here on AB)
However, as you don't like chocolate (although you might still like that stout), I'll direct you to Shepherd Neame's outstanding porter. Asda sell it as their own-brand Whitechapel porter
https://groceries.asda.com/product/bottled-ale/asda-extra-special-whitechapel-porter-premium-ale/40236
and Sainsbury's stock it as their London porterhttps://www.sainsburys.co.uk/webapp/wcs/stores/servlet/gb/groceries/all-vegan-products/sainsburys-london-porter--taste-the-difference
There's a slight hint of chocolate in the flavour but, I suspect, not enough to prevent you appreciating the quality of the ale.
Alternatively, head to Waitrose for a lovely dark wheat bear:
https://www.waitrose.com/ecom/products/weihenstephaner-dunkel-weissbier-germany/807974-175342-175343