Definitely contact them! If they say no then at least you’ve tried, and I’m sure at least 1 will take pity on you and give you a chance!
If you got a D you weren’t far off!
I actually think you should just apply, include your best work and your D, you weren’t far off and they’ll understand that! In the meantime you should take courses in art and try get work experience- after lockdown-, I want to go into teaching and I’ve been using the courses on ‘future learn’ it probably has tons of art courses! If you do these you can include it when applying or speaking to collages and they’ll know that your committed and persistent in art being what you want to do! Worst come worst resis the higher art! I’m sure you would get a better grade the second time round and it wouldn’t be too hard, even if you’ve left school just do it out if school and make your own portfolio, I know people who’ve done this although o don’t know the politics behind it!
I know this is long hope it helps!
Best of luck x